diff --git a/ChangeLog b/ChangeLog
index 041795ae13..fd85383d62 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jan 26 22:57:30 2011  CHIKANAGA Tomoyuki  <nagachika00@gmail.com>
+
+	* class.c (clone_method): add GC guard to prevent intermediate
+	  variable from GC. [Bug #4321] [ruby-dev:43107]
+
 Wed Jan 26 22:45:16 2011  Tanaka Akira  <akr@fsij.org>
 
 	* template/id.h.tmpl: parenthesize macro arguments.
diff --git a/class.c b/class.c
index 76f4ef8622..0d7623350f 100644
--- a/class.c
+++ b/class.c
@@ -129,11 +129,13 @@ VALUE rb_iseq_clone(VALUE iseqval, VALUE newcbase);
 static int
 clone_method(ID mid, const rb_method_entry_t *me, struct clone_method_data *data)
 {
+    VALUE newiseqval;
     if (me->def && me->def->type == VM_METHOD_TYPE_ISEQ) {
-	VALUE newiseqval = rb_iseq_clone(me->def->body.iseq->self, data->klass);
 	rb_iseq_t *iseq;
+	newiseqval = rb_iseq_clone(me->def->body.iseq->self, data->klass);
 	GetISeqPtr(newiseqval, iseq);
 	rb_add_method(data->klass, mid, VM_METHOD_TYPE_ISEQ, iseq, me->flag);
+	RB_GC_GUARD(newiseqval);
     }
     else {
 	rb_method_entry_set(data->klass, mid, me, me->flag);