diff --git a/ChangeLog b/ChangeLog
index ee2a8cf204..2fec8ddb72 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,12 @@
+Wed Jul  1 05:57:03 2015  Eric Wong  <e@80x24.org>
+
+	* vm_method.c (rb_add_method_iseq): add RB_GC_GUARD
+	* class.c (clone_method): remove RB_GC_GUARD
+	* struct.c (define_aref_method): ditto
+	  (define_aset_method): ditto
+	* vm.c (vm_define_method):
+	* iseq.c (rb_iseq_clone): add RB_GC_GUARD
+
 Wed Jul  1 05:43:58 2015  Eric Wong  <e@80x24.org>
 
 	* struct.c (AREF_HASH_THRESHOLD): new macro
diff --git a/class.c b/class.c
index 6ee1e084d3..6207fb7c5a 100644
--- a/class.c
+++ b/class.c
@@ -249,7 +249,6 @@ clone_method(VALUE old_klass, VALUE new_klass, ID mid, const rb_method_entry_t *
 	newiseqval = rb_iseq_clone(me->def->body.iseq.iseqptr->self, new_klass);
 	rb_vm_rewrite_cref(me->def->body.iseq.cref, old_klass, new_klass, &new_cref);
 	rb_add_method_iseq(new_klass, mid, newiseqval, new_cref, METHOD_ENTRY_VISI(me));
-	RB_GC_GUARD(newiseqval);
     }
     else {
 	rb_method_entry_set(new_klass, mid, me, METHOD_ENTRY_VISI(me));
diff --git a/iseq.c b/iseq.c
index 037df44d2c..48de119a32 100644
--- a/iseq.c
+++ b/iseq.c
@@ -1968,6 +1968,8 @@ rb_iseq_clone(VALUE iseqval, VALUE newcbase)
 	RB_OBJ_WRITTEN(iseq1->self, Qundef, iseq1->klass);
     }
 
+    RB_GC_GUARD(iseqval); /* seems necessary iff RGenGC is disabled */
+
     return newiseq;
 }
 
diff --git a/struct.c b/struct.c
index eda56733e2..b68f2a8a44 100644
--- a/struct.c
+++ b/struct.c
@@ -288,7 +288,6 @@ define_aref_method(VALUE nstr, VALUE name, VALUE off)
     VALUE iseqval = rb_method_for_self_aref(name, off, rb_vm_opt_struct_aref);
 
     rb_add_method_iseq(nstr, SYM2ID(name), iseqval, NULL, METHOD_VISI_PUBLIC);
-    RB_GC_GUARD(iseqval);
 }
 
 static void
@@ -298,7 +297,6 @@ define_aset_method(VALUE nstr, VALUE name, VALUE off)
     VALUE iseqval = rb_method_for_self_aset(name, off, rb_vm_opt_struct_aset);
 
     rb_add_method_iseq(nstr, SYM2ID(name), iseqval, NULL, METHOD_VISI_PUBLIC);
-    RB_GC_GUARD(iseqval);
 }
 
 static VALUE
diff --git a/vm.c b/vm.c
index 69b594f950..ad0d8505f7 100644
--- a/vm.c
+++ b/vm.c
@@ -2288,7 +2288,7 @@ vm_define_method(rb_thread_t *th, VALUE obj, ID id, VALUE iseqval,
     GetISeqPtr(iseqval, miseq);
 
     if (miseq->klass) {
-	RB_GC_GUARD(iseqval) = rb_iseq_clone(iseqval, 0);
+	iseqval = rb_iseq_clone(iseqval, 0);
 	GetISeqPtr(iseqval, miseq);
     }
 
diff --git a/vm_method.c b/vm_method.c
index 43b5d2aafc..5a8439649a 100644
--- a/vm_method.c
+++ b/vm_method.c
@@ -562,6 +562,7 @@ rb_add_method_iseq(VALUE klass, ID mid, VALUE iseqval, rb_cref_t *cref, rb_metho
     iseq_body.iseqptr = iseq;
     iseq_body.cref = cref;
     rb_add_method(klass, mid, VM_METHOD_TYPE_ISEQ, &iseq_body, visi);
+    RB_GC_GUARD(iseqval);
 }
 
 static rb_method_entry_t *