diff --git a/eval.c b/eval.c
index cd91a1a735..90da22503e 100644
--- a/eval.c
+++ b/eval.c
@@ -409,10 +409,6 @@ rb_frozen_class_p(VALUE klass)
       noclass:
 	Check_Type(klass, T_CLASS);
     }
-    if (FL_TEST(klass, FL_SINGLETON)) {
-	VALUE obj = rb_ivar_get(klass, id__attached__);
-	if (OBJ_FROZEN(obj)) OBJ_FREEZE(klass);
-    }
     if (OBJ_FROZEN(klass)) {
 	const char *desc;
 
diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index c7ab5ef580..b198e65625 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -1105,7 +1105,19 @@ struct RStruct {
     RBASIC(x)->flags |= RBASIC(s)->flags & FL_TAINT : 0)
 
 #define OBJ_FROZEN(x) (FL_ABLE(x) ? !!(RBASIC(x)->flags&FL_FREEZE) : 1)
-#define OBJ_FREEZE(x) FL_SET((x), FL_FREEZE)
+#define OBJ_FREEZE(x) rb_obj_freeze_inline((VALUE)x)
+
+static inline void
+rb_obj_freeze_inline(VALUE x)
+{
+    if (FL_ABLE(x)) {
+	VALUE klass = RBASIC_CLASS(x);
+	RBASIC(x)->flags |= FL_FREEZE;
+	if (FL_TEST(klass, (FL_SINGLETON|FL_FREEZE)) == FL_SINGLETON) {
+	    RBASIC(klass)->flags |= FL_FREEZE;
+	}
+    }
+}
 
 #if USE_RGENGC
 #define OBJ_PROMOTED_RAW(x)         ((RBASIC(x)->flags & (FL_PROMOTED0|FL_PROMOTED1)) == (FL_PROMOTED0|FL_PROMOTED1))