1 files changed, 2 insertions, 1 deletions
diff --git a/gc.c b/gc.c
index 4b239b634..9bbca2258 100644
--- a/gc.c
+++ b/gc.c
@@ -2069,7 +2069,8 @@ id2ref(VALUE obj, VALUE objid)
 	return ID2SYM(symid);
     }
 
-    if (!is_pointer_to_heap((void *)ptr) || BUILTIN_TYPE(ptr) >= T_VALUES) {
+    if (!is_pointer_to_heap((void *)ptr) ||
+	BUILTIN_TYPE(ptr) >= T_VALUES || BUILTIN_TYPE(ptr) == T_ICLASS) {
 	rb_raise(rb_eRangeError, "%p is not id value", p0);
     }
     if (BUILTIN_TYPE(ptr) == 0 || RBASIC(ptr)->klass == 0) {