diff --git a/modules/gdscript/gdscript_parser.cpp b/modules/gdscript/gdscript_parser.cpp
index 6ed7f097443..25a41748cc9 100644
--- a/modules/gdscript/gdscript_parser.cpp
+++ b/modules/gdscript/gdscript_parser.cpp
@@ -3494,6 +3494,10 @@ void GDScriptParser::_parse_class(ClassNode *p_class) {
 					_set_error("'class_name' is only valid for the main class namespace.");
 					return;
 				}
+				if (self_path.empty()) {
+					_set_error("'class_name' not allowed in built-in scripts.");
+					return;
+				}
 				if (tokenizer->get_token(1) != GDScriptTokenizer::TK_IDENTIFIER) {
 
 					_set_error("'class_name' syntax: 'class_name <UniqueName>'");