1 files changed, 4 insertions, 1 deletions
diff --git a/gc.c b/gc.c
index 6c230d7820..9b218934b4 100644
--- a/gc.c
+++ b/gc.c
@@ -1491,7 +1491,10 @@ internal_object_p(VALUE obj)
           case T_ZOMBIE:
             break;
           case T_CLASS:
-            if (!RBASIC(obj)->klass) break;
+            if (obj == rb_mRubyVMFrozenCore)
+                return 1;
+
+            if (!RBASIC_CLASS(obj)) break;
             if (RCLASS_SINGLETON_P(obj)) {
                 return rb_singleton_class_internal_p(obj);
             }