diff --git a/configure.ac b/configure.ac
index 47872d7ba..d71c611a9 100644
--- a/configure.ac
+++ b/configure.ac
@@ -612,11 +612,11 @@ case "$with_spidermonkey" in
 		;;
 esac
 
-for package in mozjs-45; do
+for package in mozjs-52; do
 	if test -n "$CONFIG_SPIDERMONKEY"; then
 		break
 	else
-		AC_MSG_CHECKING([for SpiderMonkey (mozjs-45) in pkg-config $package])
+		AC_MSG_CHECKING([for SpiderMonkey (mozjs-52) in pkg-config $package])
 		if $PKG_CONFIG --cflags --libs $package > /dev/null 2>&AS_MESSAGE_LOG_FD; then
 			SPIDERMONKEY_LIBS="$($PKG_CONFIG --libs $package)"
 			SPIDERMONKEY_CFLAGS="$($PKG_CONFIG --cflags $package)"
diff --git a/meson.build b/meson.build
index 777e58084..9f02215d0 100644
--- a/meson.build
+++ b/meson.build
@@ -271,7 +271,7 @@ if conf_data.get('CONFIG_BZIP2')
 endif
 
 if conf_data.get('CONFIG_ECMASCRIPT')
-    mozjsdeps = dependency('mozjs-45')
+    mozjsdeps = dependency('mozjs-52')
     deps += mozjsdeps
 endif
 
diff --git a/src/dialogs/info.c b/src/dialogs/info.c
index d4f4f7989..910d4ce23 100644
--- a/src/dialogs/info.c
+++ b/src/dialogs/info.c
@@ -232,7 +232,7 @@ get_resource_info(struct terminal *term, void *data)
 	val_add(n_("%ld refreshing", "%ld refreshing", val, term));
 	add_to_string(&info, ".\n");
 
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	add_to_string(&info, _("ECMAScript", term));
 	add_to_string(&info, ": ");
 
diff --git a/src/document/renderer.c b/src/document/renderer.c
index e49b4abc3..150e72aa8 100644
--- a/src/document/renderer.c
+++ b/src/document/renderer.c
@@ -42,7 +42,7 @@
 #include "viewer/text/vs.h"
 
 
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 /** @todo XXX: This function is de facto obsolete, since we do not need to copy
  * snippets around anymore (we process them in one go after the document is
  * loaded; gradual processing was practically impossible because the snippets
@@ -331,7 +331,7 @@ render_document(struct view_state *vs, struct document_view *doc_view,
 		vs->doc_view->used = 0; /* A bit risky, but... */
 		vs->doc_view->vs = NULL;
 		vs->doc_view = NULL;
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 		vs->ecmascript_fragile = 1; /* And is this good? ;-) */
 #endif
 	}
@@ -385,7 +385,7 @@ render_document(struct view_state *vs, struct document_view *doc_view,
 		document->css_magic = get_document_css_magic(document);
 #endif
 	}
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	if (!vs->ecmascript_fragile)
 		assert(vs->ecmascript);
 	if (!options->dump && !options->gradual_rerendering) {
diff --git a/src/ecmascript/Makefile b/src/ecmascript/Makefile
index 0e5ae66e3..69cb11227 100644
--- a/src/ecmascript/Makefile
+++ b/src/ecmascript/Makefile
@@ -4,7 +4,7 @@ INCLUDES += $(SPIDERMONKEY_CFLAGS)
 
 SUBDIRS-$(CONFIG_ECMASCRIPT_SMJS)	+= spidermonkey
 
-OBJS-$(CONFIG_ECMASCRIPT_SMJS)		+= spidermonkey.o
+OBJS-$(CONFIG_ECMASCRIPT_SMJS)		+= ecmascript.o spidermonkey.o
 
 ifeq ($(CONFIG_ECMASCRIPT_SMJS), yes)
 CONFIG_ANY_SPIDERMONKEY = yes
@@ -16,6 +16,4 @@ endif
 
 OBJS-$(CONFIG_ANY_SPIDERMONKEY) += spidermonkey-shared.o
 
-OBJS	= ecmascript.o
-
 include $(top_srcdir)/Makefile.lib
diff --git a/src/ecmascript/ecmascript.c b/src/ecmascript/ecmascript.c
index 5b48abb2b..7979f77de 100644
--- a/src/ecmascript/ecmascript.c
+++ b/src/ecmascript/ecmascript.c
@@ -5,6 +5,7 @@
 #endif
 
 #include <stdlib.h>
+#include <stdio.h>
 
 #include "elinks.h"
 
diff --git a/src/ecmascript/ecmascript.h b/src/ecmascript/ecmascript.h
index 55273fad1..0f2a3421d 100644
--- a/src/ecmascript/ecmascript.h
+++ b/src/ecmascript/ecmascript.h
@@ -53,6 +53,7 @@ struct ecmascript_interpreter {
 	 * is reloaded in another tab and then you just cause the current tab
 	 * to redraw. */
 	unsigned int onload_snippets_cache_id;
+	void *ac;
 };
 
 /* Why is the interpreter bound to {struct view_state} instead of {struct
diff --git a/src/ecmascript/meson.build b/src/ecmascript/meson.build
index af4aec2b1..d171694d8 100644
--- a/src/ecmascript/meson.build
+++ b/src/ecmascript/meson.build
@@ -1,7 +1,7 @@
 #INCLUDES += $(SPIDERMONKEY_CFLAGS)
 if conf_data.get('CONFIG_ECMASCRIPT_SMJS')
 	subdir('spidermonkey')
-	srcs += files('spidermonkey.c')
+	srcs += files('ecmascript.c', 'spidermonkey.c')
 endif
 
 if conf_data.get('CONFIG_ECMASCRIPT_SMJS')
@@ -16,4 +16,3 @@ if CONFIG_ANY_SPIDERMONKEY
 	srcs += files('spidermonkey-shared.c', 'empty.cpp')
 endif
 
-srcs += files('ecmascript.c')
diff --git a/src/ecmascript/spidermonkey-shared.c b/src/ecmascript/spidermonkey-shared.c
index 8af6d5651..b65f239cd 100644
--- a/src/ecmascript/spidermonkey-shared.c
+++ b/src/ecmascript/spidermonkey-shared.c
@@ -10,24 +10,12 @@
 #include "ecmascript/spidermonkey-shared.h"
 #include <js/Initialization.h>
 
-/** A shared runtime used for both user scripts (scripting/smjs/) and
- * scripts on web pages (ecmascript/spidermonkey/).
- *
- * SpiderMonkey has bugs that corrupt memory when multiple JSRuntimes
- * are used: https://bugzilla.mozilla.org/show_bug.cgi?id=378918 and
- * perhaps others.  */
-JSRuntime *spidermonkey_runtime;
-
 /** A JSContext that can be used in JS_SetPrivate and JS_GetPrivate
- * when no better one is available.  This context has no global
- * object, so scripts cannot be evaluated in it.
- *
- * XXX: This also works around a crash on exit.  SMJS will crash on
- * JS_DestroyRuntime if the given runtime has never had any context
- * created, which will be the case if one closes ELinks without having
- * loaded any documents.  */
-JSContext *spidermonkey_empty_context;
+- * when no better one is available.  This context has no global
+- * object, so scripts cannot be evaluated in it.
+- */
 
+JSContext *spidermonkey_empty_context;
 /** A reference count for ::spidermonkey_runtime so that modules using
  * it can be initialized and shut down in arbitrary order.  */
 static int spidermonkey_runtime_refcount;
@@ -41,32 +29,18 @@ int
 spidermonkey_runtime_addref(void)
 {
 	if (spidermonkey_runtime_refcount == 0) {
-		assert(spidermonkey_runtime == NULL);
-		assert(spidermonkey_empty_context == NULL);
-		if_assert_failed return 0;
 
 		if (!JS_Init()) {
 			return 0;
 		}
 
-		spidermonkey_runtime = JS_NewRuntime(4L * 1024L * 1024L);
-		if (!spidermonkey_runtime) return 0;
-		
-		spidermonkey_empty_context = JS_NewContext(spidermonkey_runtime,
-							   0);
+		spidermonkey_empty_context = JS_NewContext(0);
 		if (!spidermonkey_empty_context) {
-			/* Perhaps JS_DestroyRuntime will now crash
-			 * because no context was created, but there's
-			 * not much else to do.  */
-			JS_DestroyRuntime(spidermonkey_runtime);
-			spidermonkey_runtime = NULL;
 			JS_ShutDown();
 			return 0;
 		}
 	}
 
-	assert(spidermonkey_runtime);
-	assert(spidermonkey_empty_context);
 	spidermonkey_runtime_refcount++;
 	assert(spidermonkey_runtime_refcount > 0);
 	if_assert_failed { spidermonkey_runtime_refcount--; return 0; }
@@ -80,16 +54,10 @@ void
 spidermonkey_runtime_release(void)
 {
 	assert(spidermonkey_runtime_refcount > 0);
-	assert(spidermonkey_runtime);
-	assert(spidermonkey_empty_context);
-	if_assert_failed return;
 
 	--spidermonkey_runtime_refcount;
 	if (spidermonkey_runtime_refcount == 0) {
 		JS_DestroyContext(spidermonkey_empty_context);
-		spidermonkey_empty_context = NULL;
-		JS_DestroyRuntime(spidermonkey_runtime);
-		spidermonkey_runtime = NULL;
 		JS_ShutDown();
 	}
 }
diff --git a/src/ecmascript/spidermonkey.c b/src/ecmascript/spidermonkey.c
index a626eebb8..7ab712a4b 100644
--- a/src/ecmascript/spidermonkey.c
+++ b/src/ecmascript/spidermonkey.c
@@ -58,8 +58,88 @@
 
 static int js_module_init_ok;
 
+bool
+PrintError(JSContext* cx, FILE* file, JS::ConstUTF8CharsZ toStringResult,
+               JSErrorReport* report, bool reportWarnings)
+{
+    MOZ_ASSERT(report);
+
+    /* Conditionally ignore reported warnings. */
+    if (JSREPORT_IS_WARNING(report->flags) && !reportWarnings)
+        return false;
+
+    char* prefix = nullptr;
+    if (report->filename)
+        prefix = JS_smprintf("%s:", report->filename);
+    if (report->lineno) {
+        char* tmp = prefix;
+        prefix = JS_smprintf("%s%u:%u ", tmp ? tmp : "", report->lineno, report->column);
+        JS_free(cx, tmp);
+    }
+    if (JSREPORT_IS_WARNING(report->flags)) {
+        char* tmp = prefix;
+        prefix = JS_smprintf("%s%swarning: ",
+                             tmp ? tmp : "",
+                             JSREPORT_IS_STRICT(report->flags) ? "strict " : "");
+        JS_free(cx, tmp);
+    }
+
+    const char* message = toStringResult ? toStringResult.c_str() : report->message().c_str();
+
+    /* embedded newlines -- argh! */
+    const char* ctmp;
+    while ((ctmp = strchr(message, '\n')) != 0) {
+        ctmp++;
+        if (prefix)
+            fputs(prefix, file);
+        fwrite(message, 1, ctmp - message, file);
+        message = ctmp;
+    }
+
+    /* If there were no filename or lineno, the prefix might be empty */
+    if (prefix)
+        fputs(prefix, file);
+    fputs(message, file);
+
+    if (const char16_t* linebuf = report->linebuf()) {
+        size_t n = report->linebufLength();
+
+        fputs(":\n", file);
+        if (prefix)
+            fputs(prefix, file);
+
+        for (size_t i = 0; i < n; i++)
+            fputc(static_cast<char>(linebuf[i]), file);
+
+        // linebuf usually ends with a newline. If not, add one here.
+        if (n == 0 || linebuf[n-1] != '\n')
+            fputc('\n', file);
+
+        if (prefix)
+            fputs(prefix, file);
+
+        n = report->tokenOffset();
+        for (size_t i = 0, j = 0; i < n; i++) {
+            if (linebuf[i] == '\t') {
+                for (size_t k = (j + 8) & ~7; j < k; j++)
+                    fputc('.', file);
+                continue;
+            }
+            fputc('.', file);
+            j++;
+        }
+        fputc('^', file);
+    }
+    fputc('\n', file);
+    fflush(file);
+    JS_free(cx, prefix);
+    return true;
+}
+
+
+
 static void
-error_reporter(JSContext *ctx, const char *message, JSErrorReport *report)
+error_reporter(JSContext *ctx, JSErrorReport *report)
 {
 	struct ecmascript_interpreter *interpreter = JS_GetContextPrivate(ctx);
 	struct session *ses = interpreter->vs->doc_view->session;
@@ -75,6 +155,8 @@ error_reporter(JSContext *ctx, const char *message, JSErrorReport *report)
 
 	term = ses->tab->term;
 
+	PrintError(ctx, stderr, JS::ConstUTF8CharsZ(), report, true/*reportWarnings*/);
+
 #ifdef CONFIG_LEDS
 	set_led_value(ses->status.ecmascript_led, 'J');
 #endif
@@ -93,7 +175,6 @@ error_reporter(JSContext *ctx, const char *message, JSErrorReport *report)
 			strict, exception, warning, error);
 
 	add_to_string(&msg, ":\n\n");
-	add_to_string(&msg, message);
 
 	if (report->filename) {
 		prefix = JS_smprintf("%s:", report->filename);
@@ -147,25 +228,30 @@ spidermonkey_get_interpreter(struct ecmascript_interpreter *interpreter)
 	JSContext *ctx;
 	JSObject *document_obj, *forms_obj, *history_obj, *location_obj,
 	         *statusbar_obj, *menubar_obj, *navigator_obj;
-	JSAutoCompartment *ac = NULL;
 
 	assert(interpreter);
 	if (!js_module_init_ok) return NULL;
 
-	ctx = JS_NewContext(spidermonkey_runtime,
-			    8192 /* Stack allocation chunk size */);
+//	ctx = JS_NewContext(JS::DefaultHeapMaxBytes, JS::DefaultNurseryBytes);
+	ctx = JS_NewContext(8L * 1024 * 1024);
 	if (!ctx)
 		return NULL;
 	interpreter->backend_data = ctx;
 	JSAutoRequest ar(ctx);
 	JS_SetContextPrivate(ctx, interpreter);
 	//JS_SetOptions(ctx, JSOPTION_VAROBJFIX | JS_METHODJIT);
-	JS_SetErrorReporter(spidermonkey_runtime, error_reporter);
-	JS_SetInterruptCallback(spidermonkey_runtime, heartbeat_callback);
-	JS::RootedObject window_obj(ctx, JS_NewGlobalObject(ctx, &window_class, NULL, JS::DontFireOnNewGlobalHook));
+	JS::SetWarningReporter(ctx, error_reporter);
+	JS_AddInterruptCallback(ctx, heartbeat_callback);
+	JS::CompartmentOptions options;
+
+	if (!JS::InitSelfHostedCode(ctx)) {
+		return NULL;
+	}
+
+	JS::RootedObject window_obj(ctx, JS_NewGlobalObject(ctx, &window_class, NULL, JS::FireOnNewGlobalHook, options));
 
 	if (window_obj) {
-		ac = new JSAutoCompartment(ctx, window_obj);
+		interpreter->ac = new JSAutoCompartment(ctx, window_obj);
 	} else {
 		goto release_and_fail;
 	}
@@ -191,6 +277,7 @@ spidermonkey_get_interpreter(struct ecmascript_interpreter *interpreter)
 	if (!document_obj) {
 		goto release_and_fail;
 	}
+	JS_SetPrivate(document_obj, interpreter->vs);
 
 	forms_obj = spidermonkey_InitClass(ctx, document_obj, NULL,
 					   &forms_class, NULL, 0,
@@ -266,8 +353,12 @@ spidermonkey_put_interpreter(struct ecmascript_interpreter *interpreter)
 	assert(interpreter);
 	if (!js_module_init_ok) return;
 	ctx = interpreter->backend_data;
+	if (interpreter->ac) {
+		delete (JSAutoCompartment *)interpreter->ac;
+	}
 	JS_DestroyContext(ctx);
 	interpreter->backend_data = NULL;
+	interpreter->ac = nullptr;
 }
 
 
diff --git a/src/ecmascript/spidermonkey/document.c b/src/ecmascript/spidermonkey/document.c
index aca00e649..fe5bf51c6 100644
--- a/src/ecmascript/spidermonkey/document.c
+++ b/src/ecmascript/spidermonkey/document.c
@@ -50,13 +50,18 @@
 
 static bool document_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 
+JSClassOps document_ops = {
+	JS_PropertyStub, nullptr,
+	document_get_property, JS_StrictPropertyStub,
+	nullptr, nullptr, nullptr
+};
+
+
 /* Each @document_class object must have a @window_class parent.  */
 JSClass document_class = {
 	"document",
 	JSCLASS_HAS_PRIVATE,
-	JS_PropertyStub, nullptr,
-	document_get_property, JS_StrictPropertyStub,
-	nullptr, nullptr, nullptr
+	&document_ops
 };
 
 #ifdef CONFIG_COOKIES
@@ -249,16 +254,19 @@ document_set_property_title(JSContext *ctx, int argc, JS::Value *vp)
 {
 	JS::CallArgs args = CallArgsFromVp(argc, vp);
 	JS::RootedObject hobj(ctx, &args.thisv().toObject());
-	JS::RootedObject parent_win(ctx, js::GetGlobalForObjectCrossCompartment(hobj));
+//	JS::RootedObject parent_win(ctx, js::GetGlobalForObjectCrossCompartment(hobj));
 	struct view_state *vs;
 	struct document_view *doc_view;
 	struct document *document;
 
-	assert(JS_InstanceOf(ctx, parent_win, &window_class, NULL));
+	assert(JS_InstanceOf(ctx, hobj, &document_class, NULL));
 	if_assert_failed return false;
 
-	vs = JS_GetInstancePrivate(ctx, parent_win,
-				   &window_class, NULL);
+//	assert(JS_InstanceOf(ctx, parent_win, &window_class, NULL));
+//	if_assert_failed return false;
+
+	vs = JS_GetInstancePrivate(ctx, hobj,
+				   &document_class, NULL);
 	if (!vs) {
 		return false;
 	}
diff --git a/src/ecmascript/spidermonkey/form.c b/src/ecmascript/spidermonkey/form.c
index 4ba033f88..76630191c 100644
--- a/src/ecmascript/spidermonkey/form.c
+++ b/src/ecmascript/spidermonkey/form.c
@@ -66,13 +66,17 @@ static bool form_set_property_target(JSContext *ctx, unsigned int argc, JS::Valu
 
 static void form_finalize(JSFreeOp *op, JSObject *obj);
 
+static JSClassOps form_ops = {
+	JS_PropertyStub, nullptr,
+	form_get_property, JS_StrictPropertyStub,
+	nullptr, nullptr, nullptr, form_finalize
+};
+
 /* Each @form_class object must have a @document_class parent.  */
 static JSClass form_class = {
 	"form",
 	JSCLASS_HAS_PRIVATE,	/* struct form_view *, or NULL if detached */
-	JS_PropertyStub, nullptr,
-	form_get_property, JS_StrictPropertyStub,
-	nullptr, nullptr, nullptr, form_finalize
+	&form_ops
 };
 
 
@@ -86,13 +90,17 @@ static bool input_get_property(JSContext *ctx, JS::HandleObject hobj, JS::Handle
 static bool input_set_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 static void input_finalize(JSFreeOp *op, JSObject *obj);
 
+static JSClassOps input_ops = {
+	JS_PropertyStub, nullptr,
+	input_get_property, input_set_property,
+	nullptr, nullptr, nullptr, input_finalize
+};
+
 /* Each @input_class object must have a @form_class parent.  */
 static JSClass input_class = {
 	"input", /* here, we unleash ourselves */
 	JSCLASS_HAS_PRIVATE,	/* struct form_state *, or NULL if detached */
-	JS_PropertyStub, nullptr,
-	input_get_property, input_set_property,
-	nullptr, nullptr, nullptr, input_finalize
+	&input_ops
 };
 
 /* Tinyids of properties.  Use negative values to distinguish these
@@ -264,7 +272,7 @@ input_set_property_accessKey(JSContext *ctx, unsigned int argc, JS::Value *vp)
 		}
 	}
 	if (accesskey == UCS_NO_CHAR) {
-		JS_ReportError(ctx, "Invalid UTF-16 sequence");
+		JS_ReportErrorUTF8(ctx, "Invalid UTF-16 sequence");
 		return false;
 	}
 
@@ -1890,7 +1898,7 @@ spidermonkey_detach_form_state(struct form_state *fs)
 	JSObject *jsinput = fs->ecmascript_obj;
 
 	if (jsinput) {
-		JS::RootedObject r_jsinput(spidermonkey_empty_context, jsinput);
+//		JS::RootedObject r_jsinput(spidermonkey_empty_context, jsinput);
 		/* This assumes JS_GetInstancePrivate and JS_SetPrivate
 		 * cannot GC.  */
 
@@ -1898,12 +1906,12 @@ spidermonkey_detach_form_state(struct form_state *fs)
 		 * the private pointer of jsinput should be reset;
 		 * crashes seem possible either way.  Resetting it is
 		 * easiest.  */
-		assert(JS_GetInstancePrivate(spidermonkey_empty_context,
-					     r_jsinput,
-					     &input_class, NULL)
-		       == fs);
-		if_assert_failed {}
-
+//		assert(JS_GetInstancePrivate(spidermonkey_empty_context,
+//					     r_jsinput,
+//					     &input_class, NULL)
+//		       == fs);
+//		if_assert_failed {}
+//
 		JS_SetPrivate(jsinput, NULL);
 		fs->ecmascript_obj = NULL;
 	}
@@ -1957,13 +1965,17 @@ get_form_control_object(JSContext *ctx,
 static struct form_view *form_get_form_view(JSContext *ctx, JSObject *jsform, JS::Value *argv);
 static bool form_elements_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 
+static JSClassOps form_elements_ops = {
+	JS_PropertyStub, nullptr,
+	form_elements_get_property, JS_StrictPropertyStub,
+	nullptr, nullptr, nullptr, nullptr
+};
+
 /* Each @form_elements_class object must have a @form_class parent.  */
 static JSClass form_elements_class = {
 	"elements",
 	JSCLASS_HAS_PRIVATE,
-	JS_PropertyStub, nullptr,
-	form_elements_get_property, JS_StrictPropertyStub,
-	nullptr, nullptr, nullptr, nullptr
+	&form_elements_ops
 };
 
 static bool form_elements_item2(JSContext *ctx, JS::HandleObject hobj, int index, JS::MutableHandleValue hvp);
@@ -3113,7 +3125,7 @@ spidermonkey_detach_form_view(struct form_view *fv)
 	JSObject *jsform = fv->ecmascript_obj;
 
 	if (jsform) {
-		JS::RootedObject r_jsform(spidermonkey_empty_context, jsform);
+//		JS::RootedObject r_jsform(spidermonkey_empty_context, jsform);
 		/* This assumes JS_GetInstancePrivate and JS_SetPrivate
 		 * cannot GC.  */
 
@@ -3121,11 +3133,11 @@ spidermonkey_detach_form_view(struct form_view *fv)
 		 * the private pointer of jsform should be reset;
 		 * crashes seem possible either way.  Resetting it is
 		 * easiest.  */
-		assert(JS_GetInstancePrivate(spidermonkey_empty_context,
-					     r_jsform,
-					     &form_class, NULL)
-		       == fv);
-		if_assert_failed {}
+//		assert(JS_GetInstancePrivate(spidermonkey_empty_context,
+//					     r_jsform,
+//					     &form_class, NULL)
+//		       == fv);
+//		if_assert_failed {}
 
 		JS_SetPrivate(jsform, NULL);
 		fv->ecmascript_obj = NULL;
@@ -3136,13 +3148,17 @@ spidermonkey_detach_form_view(struct form_view *fv)
 static bool forms_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 static bool forms_get_property_length(JSContext *ctx, unsigned int argc, JS::Value *vp);
 
+JSClassOps forms_ops = {
+	JS_PropertyStub, nullptr,
+	forms_get_property, JS_StrictPropertyStub,
+	nullptr, nullptr, nullptr, nullptr
+};
+
 /* Each @forms_class object must have a @document_class parent.  */
 JSClass forms_class = {
 	"forms",
 	JSCLASS_HAS_PRIVATE,
-	JS_PropertyStub, nullptr,
-	forms_get_property, JS_StrictPropertyStub,
-	nullptr, nullptr, nullptr, nullptr
+	&forms_ops
 };
 
 static bool forms_item(JSContext *ctx, unsigned int argc, JS::Value *rval);
@@ -3415,6 +3431,6 @@ jsval_to_accesskey(JSContext *ctx, JS::MutableHandleValue hvp)
 			return join_utf16_surrogates(chr[0], chr[1]);
 		}
 	}
-	JS_ReportError(ctx, "Invalid UTF-16 sequence");
+	JS_ReportErrorUTF8(ctx, "Invalid UTF-16 sequence");
 	return UCS_NO_CHAR;	/* which the caller will reject */
 }
diff --git a/src/ecmascript/spidermonkey/heartbeat.c b/src/ecmascript/spidermonkey/heartbeat.c
index e66d0f496..65383bf54 100644
--- a/src/ecmascript/spidermonkey/heartbeat.c
+++ b/src/ecmascript/spidermonkey/heartbeat.c
@@ -36,6 +36,11 @@ static struct itimerval heartbeat_timer = { { 1, 0 }, { 1, 0 } };
 bool
 heartbeat_callback(JSContext *ctx)
 {
+	struct ecmascript_interpreter *interpreter = JS_GetContextPrivate(ctx);
+
+	if (!interpreter->heartbeat || interpreter->heartbeat->ttl > 0) {
+		return true;
+	}
 	return false;
 }
 
@@ -63,7 +68,7 @@ check_heartbeats(void *data)
 
 				ecmascript_timeout_dialog(term, max_exec_time);
 			}
-			JS_RequestInterruptCallback(JS_GetRuntime(hb->interpreter->backend_data));
+			JS_RequestInterruptCallback(hb->interpreter->backend_data);
 		}
 	}
 	install_signal_handler(SIGVTALRM, check_heartbeats, NULL, 1);
diff --git a/src/ecmascript/spidermonkey/location.c b/src/ecmascript/spidermonkey/location.c
index 2059f4b6f..48827afaf 100644
--- a/src/ecmascript/spidermonkey/location.c
+++ b/src/ecmascript/spidermonkey/location.c
@@ -50,14 +50,18 @@ static bool history_back(JSContext *ctx, unsigned int argc, JS::Value *rval);
 static bool history_forward(JSContext *ctx, unsigned int argc, JS::Value *rval);
 static bool history_go(JSContext *ctx, unsigned int argc, JS::Value *rval);
 
-JSClass history_class = {
-	"history",
-	JSCLASS_HAS_PRIVATE,
+JSClassOps history_ops = {
 	JS_PropertyStub, nullptr,
 	JS_PropertyStub, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr
 };
 
+JSClass history_class = {
+	"history",
+	JSCLASS_HAS_PRIVATE,
+	&history_ops
+};
+
 const spidermonkeyFunctionSpec history_funcs[] = {
 	{ "back",		history_back,		0 },
 	{ "forward",		history_forward,	0 },
@@ -134,13 +138,16 @@ history_go(JSContext *ctx, unsigned int argc, JS::Value *rval)
 static bool location_get_property_href(JSContext *ctx, unsigned int argc, JS::Value *vp);
 static bool location_set_property_href(JSContext *ctx, unsigned int argc, JS::Value *vp);
 
+JSClassOps location_ops = {
+	JS_PropertyStub, nullptr,
+	JS_PropertyStub, JS_StrictPropertyStub,
+	nullptr, nullptr, nullptr, nullptr
+};
 /* Each @location_class object must have a @window_class parent.  */
 JSClass location_class = {
 	"location",
 	JSCLASS_HAS_PRIVATE,
-	JS_PropertyStub, nullptr,
-	JS_PropertyStub, JS_StrictPropertyStub,
-	nullptr, nullptr, nullptr, nullptr
+	&location_ops
 };
 
 /* Tinyids of properties.  Use negative values to distinguish these
diff --git a/src/ecmascript/spidermonkey/navigator.c b/src/ecmascript/spidermonkey/navigator.c
index 3bbfdf79f..46c35dc1b 100644
--- a/src/ecmascript/spidermonkey/navigator.c
+++ b/src/ecmascript/spidermonkey/navigator.c
@@ -51,14 +51,18 @@ static bool navigator_get_property_language(JSContext *ctx, unsigned int argc, J
 static bool navigator_get_property_platform(JSContext *ctx, unsigned int argc, JS::Value *vp);
 static bool navigator_get_property_userAgent(JSContext *ctx, unsigned int argc, JS::Value *vp);
 
-JSClass navigator_class = {
-	"navigator",
-	JSCLASS_HAS_PRIVATE,
+JSClassOps navigator_ops = {
 	JS_PropertyStub, nullptr,
 	JS_PropertyStub, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr
 };
 
+JSClass navigator_class = {
+	"navigator",
+	JSCLASS_HAS_PRIVATE,
+	&navigator_ops
+};
+
 /* Tinyids of properties.  Use negative values to distinguish these
  * from array indexes (even though this object has no array elements).
  * ECMAScript code should not use these directly as in navigator[-1];
diff --git a/src/ecmascript/spidermonkey/unibar.c b/src/ecmascript/spidermonkey/unibar.c
index 4a20598c6..1cf8aec5c 100644
--- a/src/ecmascript/spidermonkey/unibar.c
+++ b/src/ecmascript/spidermonkey/unibar.c
@@ -48,10 +48,20 @@
 static bool unibar_get_property_visible(JSContext *ctx, unsigned int argc, JS::Value *vp);
 static bool unibar_set_property_visible(JSContext *ctx, unsigned int argc, JS::Value *vp);
 
+JSClassOps menubar_ops = {
+	JS_PropertyStub, nullptr,
+	JS_PropertyStub, JS_StrictPropertyStub,
+	nullptr, nullptr, nullptr, nullptr
+};
+
 /* Each @menubar_class object must have a @window_class parent.  */
 JSClass menubar_class = {
 	"menubar",
 	JSCLASS_HAS_PRIVATE,	/* const char * "t" */
+	&menubar_ops
+};
+
+JSClassOps statusbar_ops = {
 	JS_PropertyStub, nullptr,
 	JS_PropertyStub, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr
@@ -60,9 +70,7 @@ JSClass menubar_class = {
 JSClass statusbar_class = {
 	"statusbar",
 	JSCLASS_HAS_PRIVATE,	/* const char * "s" */
-	JS_PropertyStub, nullptr,
-	JS_PropertyStub, JS_StrictPropertyStub,
-	nullptr, nullptr, nullptr, nullptr
+	&statusbar_ops
 };
 
 /* Tinyids of properties.  Use negative values to distinguish these
diff --git a/src/ecmascript/spidermonkey/window.c b/src/ecmascript/spidermonkey/window.c
index bd4f9d630..1279e2316 100644
--- a/src/ecmascript/spidermonkey/window.c
+++ b/src/ecmascript/spidermonkey/window.c
@@ -53,14 +53,18 @@ static bool window_get_property_status(JSContext *ctx, unsigned int argc, JS::Va
 static bool window_set_property_status(JSContext *ctx, unsigned int argc, JS::Value *vp);
 static bool window_get_property_top(JSContext *ctx, unsigned int argc, JS::Value *vp);
 
-JSClass window_class = {
-	"window",
-	JSCLASS_HAS_PRIVATE | JSCLASS_GLOBAL_FLAGS,	/* struct view_state * */
+JSClassOps window_ops = {
 	JS_PropertyStub, nullptr,
 	window_get_property, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr
 };
 
+JSClass window_class = {
+	"window",
+	JSCLASS_HAS_PRIVATE | JSCLASS_GLOBAL_FLAGS,	/* struct view_state * */
+	&window_ops
+};
+
 
 /* Tinyids of properties.  Use negative values to distinguish these
  * from array indexes (even though this object has no array elements).
@@ -440,6 +444,7 @@ window_setTimeout(JSContext *ctx, unsigned int argc, JS::Value *rval)
 	if (!code)
 		return true;
 	timeout = args[1].toInt32();
+
 	if (timeout <= 0) {
 		mem_free(code);
 		return true;
diff --git a/src/main/module.c b/src/main/module.c
index 3d0ebb865..64aba901e 100644
--- a/src/main/module.c
+++ b/src/main/module.c
@@ -60,7 +60,7 @@ struct module *builtin_modules[] = {
 #ifdef CONFIG_COOKIES
 	&cookies_module,
 #endif
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	&ecmascript_module,
 #endif
 #ifdef CONFIG_FORMHIST
diff --git a/src/protocol/protocol.c b/src/protocol/protocol.c
index aecfd098a..117311a20 100644
--- a/src/protocol/protocol.c
+++ b/src/protocol/protocol.c
@@ -219,7 +219,7 @@ generic_external_protocol_handler(struct session *ses, struct uri *uri)
 
 	switch (uri->protocol) {
 	case PROTOCOL_JAVASCRIPT:
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 		ecmascript_protocol_handler(ses, uri);
 		return;
 #else
diff --git a/src/scripting/smjs/action_object.c b/src/scripting/smjs/action_object.c
index 18c6aeb7b..532d9fab8 100644
--- a/src/scripting/smjs/action_object.c
+++ b/src/scripting/smjs/action_object.c
@@ -26,9 +26,7 @@ struct smjs_action_fn_callback_hop {
 static void smjs_action_fn_finalize(JSFreeOp *op, JSObject *obj);
 static bool smjs_action_fn_callback(JSContext *ctx, unsigned int argc, JS::Value *rval);
 
-static const JSClass action_fn_class = {
-	"action_fn",
-	JSCLASS_HAS_PRIVATE,	/* struct smjs_action_fn_callback_hop * */
+static JSClassOps action_fn_ops = {
 	JS_PropertyStub, nullptr,
 	JS_PropertyStub, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr,
@@ -37,6 +35,12 @@ static const JSClass action_fn_class = {
 	smjs_action_fn_callback,
 };
 
+static const JSClass action_fn_class = {
+	"action_fn",
+	JSCLASS_HAS_PRIVATE,	/* struct smjs_action_fn_callback_hop * */
+	&action_fn_ops
+};
+
 /* @action_fn_class.finalize */
 static void
 smjs_action_fn_finalize(JSFreeOp *op, JSObject *obj)
@@ -104,7 +108,7 @@ smjs_action_fn_callback(JSContext *ctx, unsigned int argc, JS::Value *rval)
 		 *
 		 * The "%s" prevents interpretation of any percent
 		 * signs in translations.  */
-		JS_ReportError(ctx, "%s",
+		JS_ReportErrorUTF8(ctx, "%s",
 			       _("Cannot run actions in a tab that doesn't "
 				 "have the focus", hop->ses->tab->term));
 		return false; /* make JS propagate the exception */
@@ -183,14 +187,18 @@ action_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS:
 	return true;
 }
 
-static const JSClass action_class = {
-	"action",
-	0,
+static JSClassOps action_ops = {
 	JS_PropertyStub, nullptr,
 	action_get_property, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr,
 };
 
+static const JSClass action_class = {
+	"action",
+	0,
+	&action_ops
+};
+
 static JSObject *
 smjs_get_action_object(void)
 {
diff --git a/src/scripting/smjs/bookmarks.c b/src/scripting/smjs/bookmarks.c
index fcedbaba8..d32bf1c4c 100644
--- a/src/scripting/smjs/bookmarks.c
+++ b/src/scripting/smjs/bookmarks.c
@@ -20,20 +20,28 @@
 static void bookmark_finalize(JSFreeOp *op, JSObject *obj);
 static bool bookmark_folder_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 
+static JSClassOps bookmark_ops = {
+	JS_PropertyStub, nullptr,
+	JS_PropertyStub, JS_StrictPropertyStub,
+	nullptr, nullptr, nullptr, bookmark_finalize,
+};
+
 static const JSClass bookmark_class = {
 	"bookmark",
 	JSCLASS_HAS_PRIVATE,	/* struct bookmark * */
+	&bookmark_ops
+};
+
+static JSClassOps bookmark_folder_ops = {
 	JS_PropertyStub, nullptr,
-	JS_PropertyStub, JS_StrictPropertyStub,
+	bookmark_folder_get_property, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, bookmark_finalize,
 };
 
 static const JSClass bookmark_folder_class = {
 	"bookmark_folder",
 	JSCLASS_HAS_PRIVATE,	/* struct bookmark * */
-	JS_PropertyStub, nullptr,
-	bookmark_folder_get_property, JS_StrictPropertyStub,
-	nullptr, nullptr, nullptr, bookmark_finalize,
+	&bookmark_folder_ops
 };
 
 static JSObject *
diff --git a/src/scripting/smjs/cache_object.c b/src/scripting/smjs/cache_object.c
index bd6204d21..0ea15d1c8 100644
--- a/src/scripting/smjs/cache_object.c
+++ b/src/scripting/smjs/cache_object.c
@@ -17,14 +17,18 @@
 
 static void cache_entry_finalize(JSFreeOp *op, JSObject *obj);
 
-static const JSClass cache_entry_class = {
-	"cache_entry",
-	JSCLASS_HAS_PRIVATE,	/* struct cache_entry *; a weak reference */
+static JSClassOps cache_entry_ops = {
 	JS_PropertyStub, nullptr,
 	JS_PropertyStub, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, cache_entry_finalize
 };
 
+static const JSClass cache_entry_class = {
+	"cache_entry",
+	JSCLASS_HAS_PRIVATE,	/* struct cache_entry *; a weak reference */
+	&cache_entry_ops
+};
+
 /* Tinyids of properties.  Use negative values to distinguish these
  * from array indexes (even though this object has no array elements).
  * ECMAScript code should not use these directly as in cache_entry[-1];
diff --git a/src/scripting/smjs/core.c b/src/scripting/smjs/core.c
index 94285c326..cca5caecf 100644
--- a/src/scripting/smjs/core.c
+++ b/src/scripting/smjs/core.c
@@ -37,8 +37,88 @@ alert_smjs_error(unsigned char *msg)
 	                       smjs_ses, msg);
 }
 
+static bool
+PrintError(JSContext* cx, FILE* file, JS::ConstUTF8CharsZ toStringResult,
+               JSErrorReport* report, bool reportWarnings)
+{
+    MOZ_ASSERT(report);
+
+    /* Conditionally ignore reported warnings. */
+    if (JSREPORT_IS_WARNING(report->flags) && !reportWarnings)
+        return false;
+
+    char* prefix = nullptr;
+    if (report->filename)
+        prefix = JS_smprintf("%s:", report->filename);
+    if (report->lineno) {
+        char* tmp = prefix;
+        prefix = JS_smprintf("%s%u:%u ", tmp ? tmp : "", report->lineno, report->column);
+        JS_free(cx, tmp);
+    }
+    if (JSREPORT_IS_WARNING(report->flags)) {
+        char* tmp = prefix;
+        prefix = JS_smprintf("%s%swarning: ",
+                             tmp ? tmp : "",
+                             JSREPORT_IS_STRICT(report->flags) ? "strict " : "");
+        JS_free(cx, tmp);
+    }
+
+    const char* message = toStringResult ? toStringResult.c_str() : report->message().c_str();
+
+    /* embedded newlines -- argh! */
+    const char* ctmp;
+    while ((ctmp = strchr(message, '\n')) != 0) {
+        ctmp++;
+        if (prefix)
+            fputs(prefix, file);
+        fwrite(message, 1, ctmp - message, file);
+        message = ctmp;
+    }
+
+    /* If there were no filename or lineno, the prefix might be empty */
+    if (prefix)
+        fputs(prefix, file);
+    fputs(message, file);
+
+    if (const char16_t* linebuf = report->linebuf()) {
+        size_t n = report->linebufLength();
+
+        fputs(":\n", file);
+        if (prefix)
+            fputs(prefix, file);
+
+        for (size_t i = 0; i < n; i++)
+            fputc(static_cast<char>(linebuf[i]), file);
+
+        // linebuf usually ends with a newline. If not, add one here.
+        if (n == 0 || linebuf[n-1] != '\n')
+            fputc('\n', file);
+
+        if (prefix)
+            fputs(prefix, file);
+
+        n = report->tokenOffset();
+        for (size_t i = 0, j = 0; i < n; i++) {
+            if (linebuf[i] == '\t') {
+                for (size_t k = (j + 8) & ~7; j < k; j++)
+                    fputc('.', file);
+                continue;
+            }
+            fputc('.', file);
+            j++;
+        }
+        fputc('^', file);
+    }
+    fputc('\n', file);
+    fflush(file);
+    JS_free(cx, prefix);
+    return true;
+}
+
+
+
 static void
-error_reporter(JSContext *ctx, const char *message, JSErrorReport *report)
+error_reporter(JSContext *ctx, JSErrorReport *report)
 {
 	unsigned char *strict, *exception, *warning, *error;
 	struct string msg;
@@ -51,11 +131,12 @@ error_reporter(JSContext *ctx, const char *message, JSErrorReport *report)
 	warning   = JSREPORT_IS_WARNING(report->flags) ? " warning" : "";
 	error	  = !report->flags ? " error" : "";
 
+	PrintError(ctx, stderr, JS::ConstUTF8CharsZ(), report, true/*reportWarnings*/);
+
 	add_format_to_string(&msg, "A client script raised the following%s%s%s%s",
 			strict, exception, warning, error);
 
 	add_to_string(&msg, ":\n\n");
-	add_to_string(&msg, message);
 
 	add_format_to_string(&msg, "\n\n%d:%d ", report->lineno, report->column);
 
@@ -153,13 +234,13 @@ init_smjs(struct module *module)
 {
 	if (!spidermonkey_runtime_addref()) return;
 
-	smjs_ctx = JS_NewContext(spidermonkey_runtime, 8192);
+	smjs_ctx = JS_NewContext(8L * 1024 * 1024);
 	if (!smjs_ctx) {
 		spidermonkey_runtime_release();
 		return;
 	}
 
-	JS_SetErrorReporter(spidermonkey_runtime, error_reporter);
+	JS::SetWarningReporter(smjs_ctx, error_reporter);
 
 	smjs_init_global_object();
 
diff --git a/src/scripting/smjs/elinks_object.c b/src/scripting/smjs/elinks_object.c
index 9a84ca18d..50b709d6c 100644
--- a/src/scripting/smjs/elinks_object.c
+++ b/src/scripting/smjs/elinks_object.c
@@ -108,14 +108,18 @@ static const JSPropertySpec elinks_props[] = {
 static bool elinks_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 static bool elinks_set_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 
-static const JSClass elinks_class = {
-	"elinks",
-	0,
+static const JSClassOps elinks_ops = {
 	JS_PropertyStub, nullptr,
 	elinks_get_property, elinks_set_property,
 	nullptr, nullptr, nullptr, nullptr
 };
 
+static const JSClass elinks_class = {
+	"elinks",
+	0,
+	&elinks_ops
+};
+
 
 /* @elinks_class.getProperty */
 static bool
@@ -263,15 +267,12 @@ smjs_invoke_elinks_object_method(unsigned char *method, int argc, JS::Value *arg
 	assert(argv);
 
 	JS::RootedObject r_smjs_elinks_object(smjs_ctx, smjs_elinks_object);
-	JS::Value val;
-	JS::RootedValue fun(smjs_ctx, val);
+	JS::RootedValue fun(smjs_ctx);
 
 	if (false == JS_GetProperty(smjs_ctx, r_smjs_elinks_object,
-	                               method, &fun))
-		return false;
-
-	if (rval.isUndefined())
+	                               method, &fun)) {
 		return false;
+	}
 
 	return JS_CallFunctionValue(smjs_ctx, r_smjs_elinks_object, fun, args, rval);
 }
diff --git a/src/scripting/smjs/global_object.c b/src/scripting/smjs/global_object.c
index 32491b777..733d8527c 100644
--- a/src/scripting/smjs/global_object.c
+++ b/src/scripting/smjs/global_object.c
@@ -15,14 +15,17 @@ using namespace JS;
 
 JSObject *smjs_global_object;
 
-
-static const JSClass global_class = {
-	"global", JSCLASS_GLOBAL_FLAGS,
+static const JSClassOps global_ops = {
 	JS_PropertyStub, nullptr,
 	JS_PropertyStub, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr
 };
 
+static const JSClass global_class = {
+	"global", JSCLASS_GLOBAL_FLAGS,
+	&global_ops
+};
+
 static JSObject *
 smjs_get_global_object(void)
 {
@@ -30,9 +33,13 @@ smjs_get_global_object(void)
 	JSAutoCompartment *acc = NULL;
 
 	JSAutoRequest ar(smjs_ctx);
-	RootedObject jsobj(smjs_ctx);
+	JS::CompartmentOptions opts;
 
-	jsobj = JS_NewGlobalObject(smjs_ctx, (JSClass *) &global_class, NULL, JS::DontFireOnNewGlobalHook);
+	if (!JS::InitSelfHostedCode(smjs_ctx)) {
+		return NULL;
+	}
+
+	JS::RootedObject jsobj(smjs_ctx, JS_NewGlobalObject(smjs_ctx, (JSClass *) &global_class, NULL, JS::DontFireOnNewGlobalHook, opts));
 
 	if (!jsobj) return NULL;
 
diff --git a/src/scripting/smjs/globhist.c b/src/scripting/smjs/globhist.c
index 52f618ac0..28ecf8b3f 100644
--- a/src/scripting/smjs/globhist.c
+++ b/src/scripting/smjs/globhist.c
@@ -17,15 +17,19 @@ static bool smjs_globhist_item_set_property(JSContext *ctx, JS::HandleObject hob
 
 static void smjs_globhist_item_finalize(JSFreeOp *op, JSObject *obj);
 
-static const JSClass smjs_globhist_item_class = {
-	"global_history_item",
-	JSCLASS_HAS_PRIVATE,	/* struct global_history_item * */
+static const JSClassOps smjs_globhist_item_ops = {
 	JS_PropertyStub, nullptr,
 	smjs_globhist_item_get_property, smjs_globhist_item_set_property,
 	nullptr, nullptr, nullptr,
 	smjs_globhist_item_finalize,
 };
 
+static const JSClass smjs_globhist_item_class = {
+	"global_history_item",
+	JSCLASS_HAS_PRIVATE,	/* struct global_history_item * */
+	&smjs_globhist_item_ops
+};
+
 /* @smjs_globhist_item_class.finalize */
 static void
 smjs_globhist_item_finalize(JSFreeOp *op, JSObject *obj)
@@ -243,13 +247,17 @@ ret_null:
 	return true;
 }
 
-static const JSClass smjs_globhist_class = {
-	"global_history", 0,
+static const JSClassOps smjs_globhist_ops = {
 	JS_PropertyStub, nullptr,
 	smjs_globhist_get_property, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr
 };
 
+static const JSClass smjs_globhist_class = {
+	"global_history", 0,
+	&smjs_globhist_ops
+};
+
 static JSObject *
 smjs_get_globhist_object(void)
 {
diff --git a/src/scripting/smjs/hooks.c b/src/scripting/smjs/hooks.c
index 0359927a2..a52330125 100644
--- a/src/scripting/smjs/hooks.c
+++ b/src/scripting/smjs/hooks.c
@@ -27,8 +27,8 @@ script_hook_url(va_list ap, void *data)
 	unsigned char **url = va_arg(ap, unsigned char **);
 	struct session *ses = va_arg(ap, struct session *);
 	enum evhook_status ret = EVENT_HOOK_STATUS_NEXT;
-	JS::Value args[3], rval;
-	JS::RootedValue r_rval(smjs_ctx, rval);
+	JS::Value args[3];
+	JS::RootedValue r_rval(smjs_ctx);
 
 	if (*url == NULL) return EVENT_HOOK_STATUS_NEXT;
 
@@ -59,12 +59,14 @@ script_hook_pre_format_html(va_list ap, void *data)
 	struct cache_entry *cached = va_arg(ap, struct cache_entry *);
 	enum evhook_status ret = EVENT_HOOK_STATUS_NEXT;
 	JSObject *cache_entry_object, *view_state_object = NULL;
-	JS::Value args[4], rval;
-	JS::RootedValue r_rval(smjs_ctx, rval);
+	JS::Value args[4];
+	JS::RootedValue r_rval(smjs_ctx);
 
 	evhook_use_params(ses && cached);
 
-	if (!smjs_ctx || !cached->length) goto end;
+	if (!smjs_ctx || !cached->length) {
+		goto end;
+	}
 
 	smjs_ses = ses;
 
@@ -81,9 +83,10 @@ script_hook_pre_format_html(va_list ap, void *data)
 	args[3].setObject(*view_state_object);
 
 	if (true == smjs_invoke_elinks_object_method("preformat_html",
-	                                                2, args, &r_rval))
+	                                                2, args, &r_rval)) {
 		if (false == r_rval.toBoolean())
 			ret = EVENT_HOOK_STATUS_LAST;
+	}
 
 end:
 	smjs_ses = NULL;
diff --git a/src/scripting/smjs/keybinding.c b/src/scripting/smjs/keybinding.c
index 460d72b3e..5c81c4672 100644
--- a/src/scripting/smjs/keybinding.c
+++ b/src/scripting/smjs/keybinding.c
@@ -17,14 +17,18 @@ static bool keymap_get_property(JSContext *ctx, JS::HandleObject hobj, JS::Handl
 static bool keymap_set_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 static void keymap_finalize(JSFreeOp *op, JSObject *obj);
 
-static const JSClass keymap_class = {
-	"keymap",
-	JSCLASS_HAS_PRIVATE,	/* int * */
+static const JSClassOps keymap_ops = {
 	JS_PropertyStub, nullptr,
 	keymap_get_property, keymap_set_property,
 	nullptr, nullptr, nullptr, keymap_finalize,
 };
 
+static const JSClass keymap_class = {
+	"keymap",
+	JSCLASS_HAS_PRIVATE,	/* int * */
+	&keymap_ops
+};
+
 /* @keymap_class.getProperty */
 static bool
 keymap_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp)
@@ -220,14 +224,18 @@ smjs_get_keymap_object(enum keymap_id keymap_id)
 	return keymap_object;
 }
 
-static const JSClass keymaps_hash_class = {
-	"keymaps_hash",
-	JSCLASS_HAS_PRIVATE,
+static const JSClassOps keymap_hash_ops = {
 	JS_PropertyStub, nullptr,
 	JS_PropertyStub, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr,
 };
 
+static const JSClass keymaps_hash_class = {
+	"keymaps_hash",
+	JSCLASS_HAS_PRIVATE,
+	&keymap_hash_ops
+};
+
 static JSObject *
 smjs_get_keymap_hash_object(void)
 {
diff --git a/src/scripting/smjs/session_object.c b/src/scripting/smjs/session_object.c
index 8366e317f..f91e65879 100644
--- a/src/scripting/smjs/session_object.c
+++ b/src/scripting/smjs/session_object.c
@@ -35,24 +35,32 @@ static bool session_set_property(JSContext *ctx, JS::HandleObject hobj, JS::Hand
 static void session_finalize(JSFreeOp *op, JSObject *obj);
 static bool session_construct(JSContext *ctx, unsigned int argc, JS::Value *rval);
 
-static const JSClass session_class = {
-	"session",
-	JSCLASS_HAS_PRIVATE, /* struct session *; a weak reference */
+static const JSClassOps session_ops = {
 	JS_PropertyStub, nullptr,
 	session_get_property, session_set_property,
 	nullptr, nullptr, nullptr, session_finalize,
 	NULL, NULL, NULL, session_construct
 };
 
+static const JSClass session_class = {
+	"session",
+	JSCLASS_HAS_PRIVATE, /* struct session *; a weak reference */
+	&session_ops
+};
+
 static bool smjs_location_array_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 static void smjs_location_array_finalize(JSFreeOp *op, JSObject *obj);
 
+static const JSClassOps location_array_ops = {
+	JS_PropertyStub, nullptr,
+	smjs_location_array_get_property, JS_StrictPropertyStub,
+	nullptr, nullptr, nullptr, smjs_location_array_finalize,
+};
+
 static const JSClass location_array_class = {
 	"location_array",
 	JSCLASS_HAS_PRIVATE, /* struct session *; a weak reference */
-	JS_PropertyStub, nullptr,
-	smjs_location_array_get_property, JS_StrictPropertyStub,
-	nullptr, nullptr, nullptr, smjs_location_array_finalize,
+	&location_array_ops
 };
 
 /* location_array_class is the class for array object, the elements of which
@@ -1076,14 +1084,18 @@ session_array_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId h
 	return true;
 }
 
-static const JSClass session_array_class = {
-	"session_array",
-	JSCLASS_HAS_PRIVATE, /* struct terminal *term; a weak reference */
+static const JSClassOps session_array_ops = {
 	JS_PropertyStub, nullptr,
 	session_array_get_property, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr
 };
 
+static const JSClass session_array_class = {
+	"session_array",
+	JSCLASS_HAS_PRIVATE, /* struct terminal *term; a weak reference */
+	&session_array_ops
+};
+
 JSObject *
 smjs_get_session_array_object(struct terminal *term)
 {
diff --git a/src/scripting/smjs/terminal_object.c b/src/scripting/smjs/terminal_object.c
index 49506f650..b286a842b 100644
--- a/src/scripting/smjs/terminal_object.c
+++ b/src/scripting/smjs/terminal_object.c
@@ -20,14 +20,18 @@
 static bool terminal_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 static void terminal_finalize(JSFreeOp *op, JSObject *obj);
 
-static const JSClass terminal_class = {
-	"terminal",
-	JSCLASS_HAS_PRIVATE, /* struct terminal *; a weak refernce */
+static const JSClassOps terminal_ops = {
 	JS_PropertyStub, nullptr,
 	terminal_get_property, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, terminal_finalize
 };
 
+static const JSClass terminal_class = {
+	"terminal",
+	JSCLASS_HAS_PRIVATE, /* struct terminal *; a weak refernce */
+	&terminal_ops
+};
+
 enum terminal_prop {
 	TERMINAL_TAB,
 };
@@ -187,14 +191,18 @@ terminal_array_get_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId
 ;
 }
 
-static const JSClass terminal_array_class = {
-	"terminal_array",
-	0,
+static const JSClassOps terminal_array_ops = {
 	JS_PropertyStub, nullptr,
 	terminal_array_get_property, JS_StrictPropertyStub,
 	nullptr, nullptr, nullptr, nullptr
 };
 
+static const JSClass terminal_array_class = {
+	"terminal_array",
+	0,
+	&terminal_array_ops
+};
+
 /** Return an SMJS object that scripts can use an array to get terminal
  * objects. */
 static JSObject *
diff --git a/src/scripting/smjs/view_state_object.c b/src/scripting/smjs/view_state_object.c
index be3ffca9c..101c27053 100644
--- a/src/scripting/smjs/view_state_object.c
+++ b/src/scripting/smjs/view_state_object.c
@@ -24,14 +24,18 @@ static bool view_state_get_property(JSContext *ctx, JS::HandleObject hobj, JS::H
 static bool view_state_set_property(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp);
 static void view_state_finalize(JSFreeOp *op, JSObject *obj);
 
-static const JSClass view_state_class = {
-	"view_state",
-	JSCLASS_HAS_PRIVATE,	/* struct view_state * */
+static const JSClassOps view_state_ops = {
 	JS_PropertyStub, nullptr,
 	view_state_get_property, view_state_set_property,
 	nullptr, nullptr, nullptr, view_state_finalize
 };
 
+static const JSClass view_state_class = {
+	"view_state",
+	JSCLASS_HAS_PRIVATE,	/* struct view_state * */
+	&view_state_ops
+};
+
 /* Tinyids of properties.  Use negative values to distinguish these
  * from array indexes (even though this object has no array elements).
  * ECMAScript code should not use these directly as in view_state[-1];
@@ -255,22 +259,22 @@ smjs_get_view_state_object(struct view_state *vs)
 }
 
 static bool
-smjs_elinks_get_view_state(JSContext *ctx, JS::HandleObject hobj, JS::HandleId hid, JS::MutableHandleValue hvp)
+smjs_elinks_get_view_state(JSContext *ctx, unsigned int argc, JS::Value *vp)
 {
-	JSObject *vs_obj;
-	struct view_state *vs;
+	JS::CallArgs args = CallArgsFromVp(argc, vp);
+	JS::RootedObject hobj(ctx, &args.thisv().toObject());
 
-	hvp.setNull();
+	args.rval().setNull();
 
 	if (!smjs_ses || !have_location(smjs_ses)) return true;
 
-	vs = &cur_loc(smjs_ses)->vs;
+	struct view_state *vs = &cur_loc(smjs_ses)->vs;
 	if (!vs) return true;
 
-	vs_obj = smjs_get_view_state_object(vs);
+	JSObject *vs_obj = smjs_get_view_state_object(vs);
 	if (!vs_obj) return true;
 
-	hvp.setObject(*vs_obj);
+	args.rval().setObject(*vs_obj);
 
 	return true;
 }
@@ -308,6 +312,6 @@ smjs_init_view_state_interface(void)
 	JS::RootedObject r_smjs_elinks_object(smjs_ctx, smjs_elinks_object);
 
 	JS_DefineProperty(smjs_ctx, r_smjs_elinks_object, "vs", (int32_t)0,
-		(unsigned int)(JSPROP_ENUMERATE | JSPROP_PERMANENT | JSPROP_READONLY), smjs_elinks_get_view_state, JS_StrictPropertyStub
+		(unsigned int)(JSPROP_ENUMERATE | JSPROP_PERMANENT | JSPROP_READONLY), smjs_elinks_get_view_state, nullptr/*JS_StrictPropertyStub*/
 	);
 }
diff --git a/src/viewer/text/form.c b/src/viewer/text/form.c
index e55725fe0..8e77a321c 100644
--- a/src/viewer/text/form.c
+++ b/src/viewer/text/form.c
@@ -252,7 +252,7 @@ find_form_state(struct document_view *doc_view, struct el_form_control *fc)
 
 	if (n >= vs->form_info_len) {
 		int nn = n + 1;
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 		const struct form_state *const old_form_info = vs->form_info;
 #endif
 
@@ -261,7 +261,7 @@ find_form_state(struct document_view *doc_view, struct el_form_control *fc)
 		vs->form_info = fs;
 		vs->form_info_len = nn;
 
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 		/* TODO: Standard C does not allow this comparison;
 		 * if the memory to which old_form_info pointed has
 		 * been freed, then the value of the pointer itself is
@@ -275,7 +275,7 @@ find_form_state(struct document_view *doc_view, struct el_form_control *fc)
 			for (nn = 0; nn < vs->form_info_len; nn++)
 				ecmascript_moved_form_state(&vs->form_info[nn]);
 		}
-#endif /* CONFIG_ECMASCRIPT */
+#endif /* CONFIG_ECMASCRIPT_SMJS */
 	}
 	fs = &vs->form_info[n];
 
@@ -353,7 +353,7 @@ find_form_by_form_view(struct document *document, struct form_view *fv)
 void
 done_form_state(struct form_state *fs)
 {
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	ecmascript_detach_form_state(fs);
 #endif
 	mem_free_if(fs->value);
@@ -365,7 +365,7 @@ done_form_state(struct form_state *fs)
 void
 done_form_view(struct form_view *fv)
 {
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	ecmascript_detach_form_view(fv);
 #endif
 	mem_free(fv);
diff --git a/src/viewer/text/link.c b/src/viewer/text/link.c
index 1b3354eed..e7af384fd 100644
--- a/src/viewer/text/link.c
+++ b/src/viewer/text/link.c
@@ -52,7 +52,7 @@
 static int
 current_link_evhook(struct document_view *doc_view, enum script_event_hook_type type)
 {
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	struct link *link;
 	struct script_event_hook *evhook;
 
@@ -915,7 +915,7 @@ call_onsubmit_and_submit(struct session *ses, struct document_view *doc_view,
 	assert(fc->form); /* regardless of whether there is a FORM element */
 	if_assert_failed return 0;
 
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	/* If the form has multiple submit buttons, this does not
 	 * explicitly tell the ECMAScript code which of them was
 	 * pressed.  W3C DOM Level 3 doesn't seem to include such a
@@ -952,7 +952,7 @@ call_onsubmit_and_submit(struct session *ses, struct document_view *doc_view,
 			if (!res) return 1;
 		}
 	}
-#endif	/* CONFIG_ECMASCRIPT */
+#endif	/* CONFIG_ECMASCRIPT_SMJS */
 
 	uri = get_form_uri(ses, doc_view, fc);
 	if (!uri) return 0;
diff --git a/src/viewer/text/vs.c b/src/viewer/text/vs.c
index 7462cb512..fc5f9717e 100644
--- a/src/viewer/text/vs.c
+++ b/src/viewer/text/vs.c
@@ -38,7 +38,7 @@ init_vs(struct view_state *vs, struct uri *uri, int plain)
 	vs->plain = plain;
 	vs->uri = uri ? get_uri_reference(uri) : NULL;
 	vs->did_fragment = !uri->fragmentlen;
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	/* If we ever get to render this vs, give it an interpreter. */
 	vs->ecmascript_fragile = 1;
 #endif
@@ -67,7 +67,7 @@ destroy_vs(struct view_state *vs, int blast_ecmascript)
 	}
 	
 	if (vs->uri) done_uri(vs->uri);
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	if (blast_ecmascript && vs->ecmascript)
 		ecmascript_put_interpreter(vs->ecmascript);
 #endif
@@ -87,7 +87,7 @@ copy_vs(struct view_state *dst, struct view_state *src)
 
 	/* We do not copy ecmascript stuff around since it's specific for
 	 * a single location, offsprings (followups and so) nedd their own. */
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 	dst->ecmascript = NULL;
 	/* If we ever get to render this vs, give it an interpreter. */
 	dst->ecmascript_fragile = 1;
@@ -131,7 +131,7 @@ copy_vs(struct view_state *dst, struct view_state *src)
 				struct form_state *srcfs = &src->form_info[i];
 				struct form_state *dstfs = &dst->form_info[i];
 
-#ifdef CONFIG_ECMASCRIPT
+#ifdef CONFIG_ECMASCRIPT_SMJS
 				dstfs->ecmascript_obj = NULL;
 #endif
 				if (srcfs->value)
diff --git a/test/ecmascript/scroll.html b/test/ecmascript/scroll.html
index 3ddb94783..81b2216c7 100644
--- a/test/ecmascript/scroll.html
+++ b/test/ecmascript/scroll.html
@@ -6,7 +6,7 @@ function scrollText() {
 	tekst = tekst.substring(1, tekst.length) + znak;
 	return tekst.substring(0, 80);
 }
-function scroll () {
+function scroll() {
      document.title = scrollText();
      setTimeout("scroll()", 100);
 }