1 files changed, 1 insertions, 1 deletions
diff --git a/eval.c b/eval.c
index 0d74de483a..38f38de61d 100644
--- a/eval.c
+++ b/eval.c
@@ -428,7 +428,7 @@ rb_class_modify_check(VALUE klass)
     if (OBJ_FROZEN(klass)) {
         const char *desc;
 
-        if (FL_TEST(klass, FL_SINGLETON)) {
+        if (RCLASS_SINGLETON_P(klass)) {
             desc = "object";
             klass = RCLASS_ATTACHED_OBJECT(klass);
             if (!SPECIAL_CONST_P(klass)) {