diff --git a/src/ecmascript/libdom/spidermonkey/heartbeat.cpp b/src/ecmascript/libdom/spidermonkey/heartbeat.cpp
index 0b71df79e..9f6f5c0b7 100644
--- a/src/ecmascript/libdom/spidermonkey/heartbeat.cpp
+++ b/src/ecmascript/libdom/spidermonkey/heartbeat.cpp
@@ -89,6 +89,11 @@ add_heartbeat(struct ecmascript_interpreter *interpreter)
 
 	assert(interpreter);
 
+	if (interpreter->heartbeat) {
+		interpreter->heartbeat->ref_count++;
+		return interpreter->heartbeat;
+	}
+
 	if (!interpreter->vs || !interpreter->vs->doc_view)
 		ses = NULL;
 	else
@@ -99,6 +104,7 @@ add_heartbeat(struct ecmascript_interpreter *interpreter)
 
 	hb->ttl = get_opt_int("ecmascript.max_exec_time", ses);
 	hb->interpreter = interpreter;
+	hb->ref_count = 1;
 	add_to_list(heartbeats, hb);
 
 	/* Update the heartbeat timer. */
@@ -122,6 +128,10 @@ done_heartbeat(struct heartbeat *hb)
 	if (!hb) return; /* add_heartbeat returned NULL */
 	assert(hb->interpreter);
 
+	if (--hb->ref_count > 0) {
+		return;
+	}
+
 	/* Stop the heartbeat timer if this heartbeat is the only one. */
 	if (list_is_singleton(*hb)) {
 		heartbeat_timer.it_value.tv_sec = 0;
diff --git a/src/ecmascript/spidermonkey.cpp b/src/ecmascript/spidermonkey.cpp
index 3309055e5..93dc2c191 100644
--- a/src/ecmascript/spidermonkey.cpp
+++ b/src/ecmascript/spidermonkey.cpp
@@ -306,6 +306,7 @@ spidermonkey_put_interpreter(struct ecmascript_interpreter *interpreter)
 	interpreter->backend_data = NULL;
 	interpreter->ac = nullptr;
 	interpreter->ar = nullptr;
+	done_heartbeat(interpreter->heartbeat);
 }
 
 void
diff --git a/src/ecmascript/spidermonkey/heartbeat.h b/src/ecmascript/spidermonkey/heartbeat.h
index 3f2c90eba..ef03f7e78 100644
--- a/src/ecmascript/spidermonkey/heartbeat.h
+++ b/src/ecmascript/spidermonkey/heartbeat.h
@@ -13,6 +13,7 @@ struct heartbeat {
                   * second.  When it reaches 0, script execution is
                   * terminated. */
 
+        int ref_count;
         struct ecmascript_interpreter *interpreter;
 };