diff --git a/ChangeLog b/ChangeLog
index c0eb46044a..1d74a2ba72 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Sun Aug  7 23:31:32 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
+
+	* time.c (rb_strftime_alloc): raise ERANGE if width is too large.
+	  Patch by Nobuyoshi Nakada. [Bug #4457] [ruby-dev:43285]
+
+	* test/ruby/test_time.rb (class TestTime): add a test for the
+	  above change.
+
 Sun Aug  7 22:51:45 2011  KOSAKI Motohiro  <kosaki.motohiro@gmail.com>
 
 	* ext/openssl/ossl_asn1.c (decode_eoc): remove unused variables.
diff --git a/test/ruby/test_time.rb b/test/ruby/test_time.rb
index 38e567a703..1f07a8249c 100644
--- a/test/ruby/test_time.rb
+++ b/test/ruby/test_time.rb
@@ -650,6 +650,9 @@ class TestTime < Test::Unit::TestCase
 
     # [ruby-core:33985]
     assert_equal("3000000000", Time.at(3000000000).strftime('%s'))
+
+    bug4457 = '[ruby-dev:43285]'
+    assert_raise(Errno::ERANGE, bug4457) {Time.now.strftime('%8192z')}
   end
 
   def test_delegate
diff --git a/time.c b/time.c
index dd846a630c..6817c75e1e 100644
--- a/time.c
+++ b/time.c
@@ -4325,8 +4325,12 @@ rb_strftime_alloc(char **buf, const char *format,
 	 * if the buffer is 1024 times bigger than the length of the
 	 * format string, it's not failing for lack of room.
 	 */
-	if (len > 0 || size >= 1024 * flen) break;
+	if (len > 0) break;
 	xfree(*buf);
+	if (size >= 1024 * flen) {
+	    rb_sys_fail(format);
+	    break;
+	}
     }
     return len;
 }