diff --git a/src/userfunc.c b/src/userfunc.c
index e39ce6e..00e499f 100644
--- a/src/userfunc.c
+++ b/src/userfunc.c
@@ -4459,12 +4459,13 @@
 	}
     }
     // The function name must start with an upper case letter (unless it is a
-    // Vim9 class new() function or a Vim9 class private method)
+    // Vim9 class new() function or a Vim9 class private method or one of the
+    // supported Vim9 object builtin functions)
     else if (!(flags & TFN_INT)
 	    && (builtin_function(lv.ll_name, len)
 				   || (vim9script && *lv.ll_name == '_'))
 	    && !((flags & TFN_IN_CLASS)
-		&& (STRNCMP(lv.ll_name, "new", 3) == 0
+		&& (is_valid_builtin_obj_methodname(lv.ll_name)
 		    || (*lv.ll_name == '_'))))
     {
 	semsg(_(vim9script ? e_function_name_must_start_with_capital_str