diff --git a/editor/editor_help.cpp b/editor/editor_help.cpp
index 022cf82426a..bba1939f72b 100644
--- a/editor/editor_help.cpp
+++ b/editor/editor_help.cpp
@@ -3471,7 +3471,9 @@ EditorHelpHighlighter::HighlightData EditorHelpHighlighter::_get_highlight_data(
 	}
 
 	text_edits[p_language]->set_text(p_source);
-	scripts[p_language]->set_source_code(p_source);
+	if (scripts[p_language].is_valid()) { // See GH-89610.
+		scripts[p_language]->set_source_code(p_source);
+	}
 	highlighters[p_language]->_update_cache();
 
 	HighlightData result;
@@ -3561,16 +3563,18 @@ EditorHelpHighlighter::EditorHelpHighlighter() {
 #ifdef MODULE_MONO_ENABLED
 	TextEdit *csharp_text_edit = memnew(TextEdit);
 
-	Ref<CSharpScript> csharp;
-	csharp.instantiate();
+	// See GH-89610.
+	//Ref<CSharpScript> csharp;
+	//csharp.instantiate();
 
 	Ref<EditorStandardSyntaxHighlighter> csharp_highlighter;
 	csharp_highlighter.instantiate();
 	csharp_highlighter->set_text_edit(csharp_text_edit);
-	csharp_highlighter->_set_edited_resource(csharp);
+	//csharp_highlighter->_set_edited_resource(csharp);
+	csharp_highlighter->_set_script_language(CSharpLanguage::get_singleton());
 
 	text_edits[LANGUAGE_CSHARP] = csharp_text_edit;
-	scripts[LANGUAGE_CSHARP] = csharp;
+	//scripts[LANGUAGE_CSHARP] = csharp;
 	highlighters[LANGUAGE_CSHARP] = csharp_highlighter;
 #endif
 }
@@ -3578,14 +3582,10 @@ EditorHelpHighlighter::EditorHelpHighlighter() {
 EditorHelpHighlighter::~EditorHelpHighlighter() {
 #ifdef MODULE_GDSCRIPT_ENABLED
 	memdelete(text_edits[LANGUAGE_GDSCRIPT]);
-	scripts[LANGUAGE_GDSCRIPT].unref();
-	highlighters[LANGUAGE_GDSCRIPT].unref();
 #endif
 
 #ifdef MODULE_MONO_ENABLED
 	memdelete(text_edits[LANGUAGE_CSHARP]);
-	scripts[LANGUAGE_CSHARP].unref();
-	highlighters[LANGUAGE_CSHARP].unref();
 #endif
 }
 
diff --git a/editor/plugins/script_editor_plugin.cpp b/editor/plugins/script_editor_plugin.cpp
index eeb84cb79eb..6c63d9ff0dd 100644
--- a/editor/plugins/script_editor_plugin.cpp
+++ b/editor/plugins/script_editor_plugin.cpp
@@ -137,12 +137,22 @@ void EditorStandardSyntaxHighlighter::_update_cache() {
 		}
 	}
 
-	const Ref<Script> scr = _get_edited_resource();
-	if (scr.is_valid()) {
+	const ScriptLanguage *scr_lang = script_language;
+	StringName instance_base;
+
+	if (scr_lang == nullptr) {
+		const Ref<Script> scr = _get_edited_resource();
+		if (scr.is_valid()) {
+			scr_lang = scr->get_language();
+			instance_base = scr->get_instance_base_type();
+		}
+	}
+
+	if (scr_lang != nullptr) {
 		/* Core types. */
 		const Color basetype_color = EDITOR_GET("text_editor/theme/highlighting/base_type_color");
 		List<String> core_types;
-		scr->get_language()->get_core_type_words(&core_types);
+		scr_lang->get_core_type_words(&core_types);
 		for (const String &E : core_types) {
 			highlighter->add_keyword_color(E, basetype_color);
 		}
@@ -151,9 +161,9 @@ void EditorStandardSyntaxHighlighter::_update_cache() {
 		const Color keyword_color = EDITOR_GET("text_editor/theme/highlighting/keyword_color");
 		const Color control_flow_keyword_color = EDITOR_GET("text_editor/theme/highlighting/control_flow_keyword_color");
 		List<String> keywords;
-		scr->get_language()->get_reserved_words(&keywords);
+		scr_lang->get_reserved_words(&keywords);
 		for (const String &E : keywords) {
-			if (scr->get_language()->is_control_flow_keyword(E)) {
+			if (scr_lang->is_control_flow_keyword(E)) {
 				highlighter->add_keyword_color(E, control_flow_keyword_color);
 			} else {
 				highlighter->add_keyword_color(E, keyword_color);
@@ -162,7 +172,6 @@ void EditorStandardSyntaxHighlighter::_update_cache() {
 
 		/* Member types. */
 		const Color member_variable_color = EDITOR_GET("text_editor/theme/highlighting/member_variable_color");
-		StringName instance_base = scr->get_instance_base_type();
 		if (instance_base != StringName()) {
 			List<PropertyInfo> plist;
 			ClassDB::get_property_list(instance_base, &plist);
@@ -187,7 +196,7 @@ void EditorStandardSyntaxHighlighter::_update_cache() {
 		/* Comments */
 		const Color comment_color = EDITOR_GET("text_editor/theme/highlighting/comment_color");
 		List<String> comments;
-		scr->get_language()->get_comment_delimiters(&comments);
+		scr_lang->get_comment_delimiters(&comments);
 		for (const String &comment : comments) {
 			String beg = comment.get_slice(" ", 0);
 			String end = comment.get_slice_count(" ") > 1 ? comment.get_slice(" ", 1) : String();
@@ -197,7 +206,7 @@ void EditorStandardSyntaxHighlighter::_update_cache() {
 		/* Doc comments */
 		const Color doc_comment_color = EDITOR_GET("text_editor/theme/highlighting/doc_comment_color");
 		List<String> doc_comments;
-		scr->get_language()->get_doc_comment_delimiters(&doc_comments);
+		scr_lang->get_doc_comment_delimiters(&doc_comments);
 		for (const String &doc_comment : doc_comments) {
 			String beg = doc_comment.get_slice(" ", 0);
 			String end = doc_comment.get_slice_count(" ") > 1 ? doc_comment.get_slice(" ", 1) : String();
@@ -207,7 +216,7 @@ void EditorStandardSyntaxHighlighter::_update_cache() {
 		/* Strings */
 		const Color string_color = EDITOR_GET("text_editor/theme/highlighting/string_color");
 		List<String> strings;
-		scr->get_language()->get_string_delimiters(&strings);
+		scr_lang->get_string_delimiters(&strings);
 		for (const String &string : strings) {
 			String beg = string.get_slice(" ", 0);
 			String end = string.get_slice_count(" ") > 1 ? string.get_slice(" ", 1) : String();
diff --git a/editor/plugins/script_editor_plugin.h b/editor/plugins/script_editor_plugin.h
index 4fff7248668..0252e10b43d 100644
--- a/editor/plugins/script_editor_plugin.h
+++ b/editor/plugins/script_editor_plugin.h
@@ -78,6 +78,7 @@ class EditorStandardSyntaxHighlighter : public EditorSyntaxHighlighter {
 
 private:
 	Ref<CodeHighlighter> highlighter;
+	ScriptLanguage *script_language = nullptr; // See GH-89610.
 
 public:
 	virtual void _update_cache() override;
@@ -87,6 +88,8 @@ public:
 
 	virtual Ref<EditorSyntaxHighlighter> _create() const override;
 
+	void _set_script_language(ScriptLanguage *p_script_language) { script_language = p_script_language; }
+
 	EditorStandardSyntaxHighlighter() { highlighter.instantiate(); }
 };