diff --git a/ChangeLog b/ChangeLog
index 7c89f51ccf..009aa1d678 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,16 @@
+Wed Jun  3 20:07:07 2015  Koichi Sasada  <ko1@atdot.net>
+
+	* class.c (clone_method): remove redundant check for me->def != NULL.
+	  Now, all `me` have `me->def`.
+
+	* proc.c (rb_method_entry_location): ditto.
+
+	* vm.c (rb_vm_check_redefinition_opt_method): ditto.
+
+	* vm.c (add_opt_method): ditto.
+
+	* vm_eval.c (vm_call0_body): ditto.
+
 Wed Jun  3 19:24:12 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_core.h: rename enum missing_reason to enum method_missing_reason.
diff --git a/class.c b/class.c
index e4b6cfde3e..da41d85023 100644
--- a/class.c
+++ b/class.c
@@ -243,21 +243,16 @@ rb_class_new(VALUE super)
 static void
 clone_method(VALUE klass, ID mid, const rb_method_entry_t *me)
 {
-    if (me->def) {
-	if (me->def->type == VM_METHOD_TYPE_ISEQ) {
-	    VALUE newiseqval;
-	    rb_cref_t *new_cref;
-	    newiseqval = rb_iseq_clone(me->def->body.iseq.iseqptr->self, klass);
-	    rb_vm_rewrite_cref_stack(me->def->body.iseq.cref, me->klass, klass, &new_cref);
-	    rb_add_method_iseq(klass, mid, newiseqval, new_cref, me->def->flags.visi);
-	    RB_GC_GUARD(newiseqval);
-	}
-	else {
-	    rb_method_entry_set(klass, mid, me, me->def->flags.visi);
-	}
+    if (me->def->type == VM_METHOD_TYPE_ISEQ) {
+	VALUE newiseqval;
+	rb_cref_t *new_cref;
+	newiseqval = rb_iseq_clone(me->def->body.iseq.iseqptr->self, klass);
+	rb_vm_rewrite_cref_stack(me->def->body.iseq.cref, me->klass, klass, &new_cref);
+	rb_add_method_iseq(klass, mid, newiseqval, new_cref, me->def->flags.visi);
+	RB_GC_GUARD(newiseqval);
     }
     else {
-	rb_bug("clone_method: unsupported");
+	rb_method_entry_set(klass, mid, me, me->def->flags.visi);
     }
 }
 
diff --git a/proc.c b/proc.c
index a661cb3d3b..950a02a206 100644
--- a/proc.c
+++ b/proc.c
@@ -2239,7 +2239,7 @@ method_def_location(const rb_method_definition_t *def)
 VALUE
 rb_method_entry_location(const rb_method_entry_t *me)
 {
-    if (!me || !me->def) return Qnil;
+    if (!me) return Qnil;
     return method_def_location(me->def);
 }
 
diff --git a/vm.c b/vm.c
index 0702e8a39e..a772206aeb 100644
--- a/vm.c
+++ b/vm.c
@@ -1237,7 +1237,7 @@ static void
 rb_vm_check_redefinition_opt_method(const rb_method_entry_t *me, VALUE klass)
 {
     st_data_t bop;
-    if (!me->def || me->def->type == VM_METHOD_TYPE_CFUNC) {
+    if (me->def->type == VM_METHOD_TYPE_CFUNC) {
 	if (st_lookup(vm_opt_method_table, (st_data_t)me, &bop)) {
 	    int flag = vm_redefinition_check_flag(klass);
 
@@ -1272,8 +1272,7 @@ add_opt_method(VALUE klass, ID mid, VALUE bop)
 {
     rb_method_entry_t *me = rb_method_entry_at(klass, mid);
 
-    if (me && me->def &&
-	me->def->type == VM_METHOD_TYPE_CFUNC) {
+    if (me && me->def->type == VM_METHOD_TYPE_CFUNC) {
 	st_insert(vm_opt_method_table, (st_data_t)me, (st_data_t)bop);
     }
     else {
diff --git a/vm_eval.c b/vm_eval.c
index bd7d76214b..cd8e75a657 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -153,8 +153,6 @@ vm_call0_body(rb_thread_t* th, rb_call_info_t *ci, const VALUE *argv)
 {
     VALUE ret;
 
-    if (!ci->me->def) return Qnil;
-
     if (th->passed_block) {
 	ci->blockptr = (rb_block_t *)th->passed_block;
 	th->passed_block = 0;
@@ -213,7 +211,6 @@ vm_call0_body(rb_thread_t* th, rb_call_info_t *ci, const VALUE *argv)
 		goto success;
 	    }
 	    RUBY_VM_CHECK_INTS(th);
-	    if (!ci->me->def) return Qnil;
 	    goto again;
 	}
       case VM_METHOD_TYPE_ALIAS: