diff --git a/ChangeLog b/ChangeLog
index 7bb45d2f51..b86496c8b5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sun Oct 11 06:21:50 2015  Koichi Sasada  <ko1@atdot.net>
+
+	* vm_eval.c, internal.h (rb_yield_1): added for performance which
+	  doesn't check Qundef.
+
+	* numeric.c (int_dotimes): use rb_yield_1.
+
 Sun Oct 11 06:19:49 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_insnhelper.c (vm_call_iseq_setup_normal): setup sp first
diff --git a/internal.h b/internal.h
index 00fbabbf93..232218634d 100644
--- a/internal.h
+++ b/internal.h
@@ -1192,6 +1192,7 @@ typedef void rb_check_funcall_hook(int, VALUE, ID, int, const VALUE *, VALUE);
 VALUE rb_check_funcall_with_hook(VALUE recv, ID mid, int argc, const VALUE *argv,
 				 rb_check_funcall_hook *hook, VALUE arg);
 VALUE rb_catch_protect(VALUE t, rb_block_call_func *func, VALUE data, int *stateptr);
+VALUE rb_yield_1(VALUE val);
 
 /* vm_insnhelper.c */
 VALUE rb_equal_opt(VALUE obj1, VALUE obj2);
diff --git a/numeric.c b/numeric.c
index ec12b3ac76..ad3b45c804 100644
--- a/numeric.c
+++ b/numeric.c
@@ -3949,7 +3949,7 @@ int_dotimes(VALUE num)
 
 	end = FIX2LONG(num);
 	for (i=0; i<end; i++) {
-	    rb_yield(LONG2FIX(i));
+	    rb_yield_1(LONG2FIX(i));
 	}
     }
     else {
diff --git a/vm_eval.c b/vm_eval.c
index 0abbcc2094..780a83bba1 100644
--- a/vm_eval.c
+++ b/vm_eval.c
@@ -999,6 +999,12 @@ rb_yield_0(int argc, const VALUE * argv)
     return vm_yield(GET_THREAD(), argc, argv);
 }
 
+VALUE
+rb_yield_1(VALUE val)
+{
+    return rb_yield_0(1, &val);
+}
+
 VALUE
 rb_yield(VALUE val)
 {
@@ -1006,7 +1012,7 @@ rb_yield(VALUE val)
 	return rb_yield_0(0, 0);
     }
     else {
-	return rb_yield_0(1, &val);
+	return rb_yield_1(val);
     }
 }