diff --git a/src/bookmarks/dialogs.c b/src/bookmarks/dialogs.c
index 66211089..4d32b1f5 100644
--- a/src/bookmarks/dialogs.c
+++ b/src/bookmarks/dialogs.c
@@ -556,7 +556,7 @@ test_search(struct listbox_item *item, void *data_, int *offset)
 		assert(ctx->title && ctx->url);
 
 		ctx->found = (*ctx->title && strcasestr(bm->title, ctx->title))
-			     || (*ctx->url && strcasestr(bm->url, ctx->url));
+			     || (*ctx->url && c_strcasestr(bm->url, ctx->url));
 
 		if (ctx->found) *offset = 0;
 	}
diff --git a/src/cache/dialogs.c b/src/cache/dialogs.c
index 8e5ff73a..f7550238 100644
--- a/src/cache/dialogs.c
+++ b/src/cache/dialogs.c
@@ -175,8 +175,8 @@ match_cache_entry(struct listbox_item *item, struct terminal *term,
 {
 	struct cache_entry *cached = item->udata;
 
-	if (strcasestr(struri(cached->uri), text)
-	    || (cached->head && strcasestr(cached->head, text)))
+	if (c_strcasestr(struri(cached->uri), text)
+	    || (cached->head && c_strcasestr(cached->head, text)))
 		return LISTBOX_MATCH_OK;
 
 	return LISTBOX_MATCH_NO;
diff --git a/src/config/kbdbind.c b/src/config/kbdbind.c
index da04cf65..8c495f49 100644
--- a/src/config/kbdbind.c
+++ b/src/config/kbdbind.c
@@ -18,6 +18,7 @@
 #include "main/event.h"
 #include "main/module.h"
 #include "terminal/kbd.h"
+#include "util/conv.h"
 #include "util/memory.h"
 #include "util/string.h"
 
diff --git a/src/document/html/parser.c b/src/document/html/parser.c
index 81b59091..4d8c1114 100644
--- a/src/document/html/parser.c
+++ b/src/document/html/parser.c
@@ -337,7 +337,7 @@ search_for_url_param(unsigned char *str, unsigned char **ret)
 	/* Returns now if string @str is empty. */
 	if (!*str) return HEADER_PARAM_NOT_FOUND;
 
-	p = strcasestr(str, "url");
+	p = c_strcasestr(str, "url");
 	if (!p) return HEADER_PARAM_NOT_FOUND;
 	p += 3;
 
diff --git a/src/document/html/parser/link.c b/src/document/html/parser/link.c
index 9e5c66d6..05de8259 100644
--- a/src/document/html/parser/link.c
+++ b/src/document/html/parser/link.c
@@ -762,21 +762,21 @@ html_link_parse(struct html_context *html_context, unsigned char *a,
 			return 1;
 		}
 
-	if (strcasestr(link->name, "icon") ||
-	   (link->content_type && strcasestr(link->content_type, "icon"))) {
+	if (c_strcasestr(link->name, "icon") ||
+	   (link->content_type && c_strcasestr(link->content_type, "icon"))) {
 		link->type = LT_ICON;
 
-	} else if (strcasestr(link->name, "alternate")) {
+	} else if (c_strcasestr(link->name, "alternate")) {
 		link->type = LT_ALTERNATE;
 		if (link->lang)
 			link->type = LT_ALTERNATE_LANG;
-		else if (strcasestr(link->name, "stylesheet") ||
-			 (link->content_type && strcasestr(link->content_type, "css")))
+		else if (c_strcasestr(link->name, "stylesheet") ||
+			 (link->content_type && c_strcasestr(link->content_type, "css")))
 			link->type = LT_ALTERNATE_STYLESHEET;
 		else if (link->media)
 			link->type = LT_ALTERNATE_MEDIA;
 
-	} else if (link->content_type && strcasestr(link->content_type, "css")) {
+	} else if (link->content_type && c_strcasestr(link->content_type, "css")) {
 		link->type = LT_STYLESHEET;
 	}
 
diff --git a/src/ecmascript/see/document.c b/src/ecmascript/see/document.c
index 3e4fd5d2..3287146e 100644
--- a/src/ecmascript/see/document.c
+++ b/src/ecmascript/see/document.c
@@ -152,7 +152,7 @@ document_get(struct SEE_interpreter *interp, struct SEE_object *o,
 		if (!string) return;
 
 		foreach (form, document->forms) {
-			if (!form->name || strcasecmp(string, form->name))
+			if (!form->name || c_strcasecmp(string, form->name))
 				continue;
 			form_view = find_form_view(doc_view, form);
 			form_object = js_get_form_object(interp, doc, form_view);
diff --git a/src/ecmascript/see/form.c b/src/ecmascript/see/form.c
index 40f3e1ae..0724e115 100644
--- a/src/ecmascript/see/form.c
+++ b/src/ecmascript/see/form.c
@@ -689,7 +689,7 @@ js_form_elems_namedItem(struct SEE_interpreter *interp, struct SEE_object *self,
 		return;
 
 	foreach (fc, form->items) {
-		if ((fc->id && !strcasecmp(string, fc->id)) || (fc->name && !strcasecmp(string, fc->name))) {
+		if ((fc->id && !c_strcasecmp(string, fc->id)) || (fc->name && !c_strcasecmp(string, fc->name))) {
 			struct form_state *fs = find_form_state(doc_view, fc);
 
 			if (fs) {
@@ -815,7 +815,7 @@ js_forms_namedItem(struct SEE_interpreter *interp, struct SEE_object *self,
 	if (!string)
 		return;
 	foreach (form, document->forms) {
-		if (form->name && !strcasecmp(string, form->name)) {
+		if (form->name && !c_strcasecmp(string, form->name)) {
 			struct form_view *fv = find_form_view(doc_view, form);
 			struct js_form *obj = js_get_form_object(interp,
 			 doc, fv);
@@ -952,7 +952,7 @@ form_get(struct SEE_interpreter *interp, struct SEE_object *o,
 			struct js_input *fcobj = NULL;
 			struct form_state *fs;
 
-			if ((!fc->id || strcasecmp(string, fc->id)) && (!fc->name || strcasecmp(string, fc->name)))
+			if ((!fc->id || c_strcasecmp(string, fc->id)) && (!fc->name || c_strcasecmp(string, fc->name)))
 				continue;
 			fs = find_form_state(doc_view, fc);
 			if (fs) {
@@ -989,19 +989,19 @@ form_put(struct SEE_interpreter *interp, struct SEE_object *o,
 			mem_free_set(&form->action, string);
 		}
 	} else if (p == s_encoding) {
-		if (!strcasecmp(string, "application/x-www-form-urlencoded")) {
+		if (!c_strcasecmp(string, "application/x-www-form-urlencoded")) {
 			form->method = form->method == FORM_METHOD_GET ? FORM_METHOD_GET
 			                                               : FORM_METHOD_POST;
-		} else if (!strcasecmp(string, "multipart/form-data")) {
+		} else if (!c_strcasecmp(string, "multipart/form-data")) {
 			form->method = FORM_METHOD_POST_MP;
-		} else if (!strcasecmp(string, "text/plain")) {
+		} else if (!c_strcasecmp(string, "text/plain")) {
 			form->method = FORM_METHOD_POST_TEXT_PLAIN;
 		}
 		mem_free(string);
 	} else if (p == s_method) {
-		if (!strcasecmp(string, "GET")) {
+		if (!c_strcasecmp(string, "GET")) {
 			form->method = FORM_METHOD_GET;
-		} else if (!strcasecmp(string, "POST")) {
+		} else if (!c_strcasecmp(string, "POST")) {
 			form->method = FORM_METHOD_POST;
 		}
 		mem_free(string);
diff --git a/src/ecmascript/see/window.c b/src/ecmascript/see/window.c
index 1f37944c..5b2b4449 100644
--- a/src/ecmascript/see/window.c
+++ b/src/ecmascript/see/window.c
@@ -304,7 +304,7 @@ js_window_open(struct SEE_interpreter *interp, struct SEE_object *self,
 		return;
 	}
 
-	if (frame && *frame && strcasecmp(frame, "_blank")) {
+	if (frame && *frame && c_strcasecmp(frame, "_blank")) {
 		struct delayed_open *deo = mem_calloc(1, sizeof(*deo));
 
 		if (deo) {
diff --git a/src/globhist/globhist.c b/src/globhist/globhist.c
index 7f1d7b2b..eef21d06 100644
--- a/src/globhist/globhist.c
+++ b/src/globhist/globhist.c
@@ -318,7 +318,7 @@ globhist_simple_search(unsigned char *search_url, unsigned char *search_title)
 		if ((*search_title
 		     && strcasestr(history_item->title, search_title))
 		    || (*search_url
-			&& strcasestr(history_item->url, search_url))) {
+			&& c_strcasestr(history_item->url, search_url))) {
 			history_item->box_item->visible = 1;
 		} else {
 			history_item->box_item->visible = 0;
diff --git a/src/mime/mime.c b/src/mime/mime.c
index 81d64820..c323290f 100644
--- a/src/mime/mime.c
+++ b/src/mime/mime.c
@@ -249,7 +249,7 @@ get_fragment_content_type(struct cache_entry *cached)
 	if (!sample)
 		return NULL;
 
-	if (strcasestr(sample, "<html>"))
+	if (c_strcasestr(sample, "<html>"))
 		ctype = stracpy("text/html");
 
 	mem_free(sample);
@@ -291,7 +291,7 @@ get_content_type(struct cache_entry *cached)
 		 * is with default (via option system) and mimetypes resolving
 		 * doing that option and hash lookup will not be easy to
 		 * convert. --jonas */
-		convert_to_lowercase(extension, strlen(extension));
+		convert_to_lowercase_locale_indep(extension, strlen(extension));
 
 		ctype = get_extension_content_type(extension);
 		mem_free(extension);
diff --git a/src/protocol/http/http.c b/src/protocol/http/http.c
index 20c53197..2271adb3 100644
--- a/src/protocol/http/http.c
+++ b/src/protocol/http/http.c
@@ -1424,13 +1424,13 @@ check_http_authentication(struct connection *conn, struct uri *uri,
 			break;
 		}
 #ifdef CONFIG_GSSAPI
-		else if (!strncasecmp(d, HTTPNEG_GSS_STR, HTTPNEG_GSS_STRLEN)) {
+		else if (!c_strncasecmp(d, HTTPNEG_GSS_STR, HTTPNEG_GSS_STRLEN)) {
 			if (http_negotiate_input(conn, uri, HTTPNEG_GSS, str)==0)
 				ret = 1;
 			mem_free(d);
 			break;
 		}
-		else if (!strncasecmp(d, HTTPNEG_NEG_STR, HTTPNEG_NEG_STRLEN)) {
+		else if (!c_strncasecmp(d, HTTPNEG_NEG_STR, HTTPNEG_NEG_STRLEN)) {
 			if (http_negotiate_input(conn, uri, HTTPNEG_NEG, str)==0)
 				ret = 1;
 			mem_free(d);
@@ -1874,7 +1874,7 @@ again:
 		if (file_encoding != ENCODING_GZIP
 		    && (!c_strcasecmp(d, "gzip") || !c_strcasecmp(d, "x-gzip")))
 		    	conn->content_encoding = ENCODING_GZIP;
-		if (!strcasecmp(d, "deflate") || !strcasecmp(d, "x-deflate"))
+		if (!c_strcasecmp(d, "deflate") || !c_strcasecmp(d, "x-deflate"))
 			conn->content_encoding = ENCODING_DEFLATE;
 #endif
 
@@ -1886,7 +1886,7 @@ again:
 
 #ifdef CONFIG_LZMA
 		if (file_encoding != ENCODING_LZMA
-		    && (!strcasecmp(d, "lzma") || !strcasecmp(d, "x-lzma")))
+		    && (!c_strcasecmp(d, "lzma") || !c_strcasecmp(d, "x-lzma")))
 			conn->content_encoding = ENCODING_LZMA;
 #endif
 		mem_free(d);
diff --git a/src/protocol/proxy.c b/src/protocol/proxy.c
index c9daafd6..f6b1e7a9 100644
--- a/src/protocol/proxy.c
+++ b/src/protocol/proxy.c
@@ -37,7 +37,7 @@ proxy_probe_no_proxy(unsigned char *url, unsigned char *no_proxy)
 		skip_space(no_proxy);
 		if (jumper) *jumper = '\0';
 
-		if (strcasestr(url, no_proxy)) {
+		if (c_strcasestr(url, no_proxy)) {
 			if (jumper) *jumper = ',';
 			if (slash) *slash = '/';
 			return 1;
diff --git a/src/protocol/uri.c b/src/protocol/uri.c
index fd8ca7d4..5e23ea27 100644
--- a/src/protocol/uri.c
+++ b/src/protocol/uri.c
@@ -274,7 +274,7 @@ parse_uri(struct uri *uri, unsigned char *uristring)
 
 		/* A bit of a special case, but using the "normal" host
 		 * parsing seems a bit scary at this point. (see bug 107). */
-		if (datalen > 9 && !strncasecmp(prefix_end, "localhost/", 10)) {
+		if (datalen > 9 && !c_strncasecmp(prefix_end, "localhost/", 10)) {
 			prefix_end += 9;
 			datalen -= 9;
 		}
@@ -711,8 +711,8 @@ normalize_uri(struct uri *uri, unsigned char *uristring)
 		 * get_translated_uri() through translate_url() calls this
 		 * function and then it already works on and modifies an
 		 * allocated copy. */
-		convert_to_lowercase(uri->string, uri->protocollen);
-		if (uri->hostlen) convert_to_lowercase(uri->host, uri->hostlen);
+		convert_to_lowercase_locale_indep(uri->string, uri->protocollen);
+		if (uri->hostlen) convert_to_lowercase_locale_indep(uri->host, uri->hostlen);
 
 		parse = 1;
 		parse_string = uri->data;
diff --git a/src/protocol/user.c b/src/protocol/user.c
index f0bcc5db..8efc79cb 100644
--- a/src/protocol/user.c
+++ b/src/protocol/user.c
@@ -104,7 +104,7 @@ get_user_program(struct terminal *term, unsigned char *progid, int progidlen)
 
 	/* Now add lowercased progid part. Delicious. */
 	add_bytes_to_string(&name, progid, progidlen);
-	convert_to_lowercase(&name.source[sizeof("protocol.user.") - 1], progidlen);
+	convert_to_lowercase_locale_indep(&name.source[sizeof("protocol.user.") - 1], progidlen);
 
 	add_char_to_string(&name, '.');
 	add_to_string(&name, get_system_str(xwin));
diff --git a/src/util/conv.c b/src/util/conv.c
index 13e9f87b..7ca0dc63 100644
--- a/src/util/conv.c
+++ b/src/util/conv.c
@@ -411,7 +411,7 @@ strtolx(unsigned char *str, unsigned char **end)
 	if (errno) return 0;
 	if (!*end) return num;
 
-	postfix = toupper(**end);
+	postfix = c_toupper(**end);
 	if (postfix == 'K') {
 		(*end)++;
 		if (num < -INT_MAX / 1024) return -INT_MAX;
diff --git a/src/util/string.c b/src/util/string.c
index d4ef1c63..0d0cbb9f 100644
--- a/src/util/string.c
+++ b/src/util/string.c
@@ -320,6 +320,25 @@ int c_strncasecmp (const char *s1, const char *s2, size_t n)
     return (c1 > c2 ? 1 : c1 < c2 ? -1 : 0);
 }
 
+/* c_strcasestr - adapted from src/osdep/stub.c */
+char * c_strcasestr(const char *haystack, const char *needle)
+{
+	size_t haystack_length = strlen(haystack);
+	size_t needle_length = strlen(needle);
+	int i;
+
+	if (haystack_length < needle_length)
+		return NULL;
+
+	for (i = haystack_length - needle_length + 1; i; i--) {
+		if (!c_strncasecmp(haystack, needle, needle_length))
+			return (char *) haystack;
+		haystack++;
+	}
+
+	return NULL;
+}
+
 /* The new string utilities: */
 
 /* TODO Currently most of the functions use add_bytes_to_string() as a backend
diff --git a/src/util/string.h b/src/util/string.h
index 243a348c..bfce8976 100644
--- a/src/util/string.h
+++ b/src/util/string.h
@@ -111,6 +111,9 @@ int elinks_strlcasecmp(const unsigned char *s1, size_t n1,
 int c_strcasecmp(const char *s1, const char *s2);
 int c_strncasecmp(const char *s1, const char *s2, size_t n);
 
+/* strcasestr function which works as if it is in the C locale. */
+char * c_strcasestr(const char *haystack, const char *needle);
+
 /** @} */