diff --git a/ChangeLog b/ChangeLog
index 70eb12bab0..15da525661 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,7 @@
+Wed Oct  7 17:30:50 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* string.c (rb_str_times): optimize for the argument 0 and 1.
+
 Wed Oct  7 01:20:46 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* gc.h, gc.c: introduce new debug function rb_obj_info_dump(VALUE obj)
diff --git a/string.c b/string.c
index 5b556679c7..a164c34492 100644
--- a/string.c
+++ b/string.c
@@ -1598,6 +1598,15 @@ rb_str_times(VALUE str, VALUE times)
     char *ptr2;
     int termlen;
 
+    if (times == INT2FIX(1)) {
+	return rb_str_dup(str);
+    }
+    if (times == INT2FIX(0)) {
+	str2 = str_alloc(rb_obj_class(str));
+	rb_enc_copy(str2, str);
+	OBJ_INFECT(str2, str);
+	return str2;
+    }
     len = NUM2LONG(times);
     if (len < 0) {
 	rb_raise(rb_eArgError, "negative argument");