diff --git a/ChangeLog b/ChangeLog
index 2ec5224307..0699c13101 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Tue Jul  7 15:02:18 2015  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* file.c (rb_str_normalize_ospath): skip invalid byte sequence not
+	  to loop infinitely.  this case usually does not happen as the
+	  input name should come from real file systems.
+
 Tue Jul  7 14:40:08 2015  Koichi Sasada  <ko1@atdot.net>
 
 	* vm_backtrace.c: remove debug flag introduced accidentaly.
diff --git a/file.c b/file.c
index 96b89e55c1..1adbe76802 100644
--- a/file.c
+++ b/file.c
@@ -294,6 +294,8 @@ rb_str_normalize_ospath(const char *ptr, long len)
 	    rb_str_append(str, rb_str_normalize_ospath0(p1, p-p1));
 	    rb_str_cat2(str, "\xEF\xBF\xBD");
 	    p += 1;
+	    p1 = p;
+	    continue;
 	}
 	l = MBCLEN_CHARFOUND_LEN(r);
 	c = rb_enc_mbc_to_codepoint(p, e, enc);
diff --git a/test/-ext-/string/test_normalize.rb b/test/-ext-/string/test_normalize.rb
index 283ca93db7..83bbfd3011 100644
--- a/test/-ext-/string/test_normalize.rb
+++ b/test/-ext-/string/test_normalize.rb
@@ -59,7 +59,6 @@ class Test_StringNormalize < Test::Unit::TestCase
       assert_equal expected, result,
         "#{expected.dump} is expected but #{src.dump}"
     end
-  rescue NotImplementedError
   end
 
   def test_not_normalize_kc
@@ -79,7 +78,6 @@ class Test_StringNormalize < Test::Unit::TestCase
       assert_equal src, result,
         "#{src.dump} is expected not to be normalized, but #{result.dump}"
     end
-  rescue NotImplementedError
   end
 
   def test_dont_normalize_hfsplus
@@ -101,6 +99,11 @@ class Test_StringNormalize < Test::Unit::TestCase
       assert_equal src, result,
         "#{src.dump} is expected not to be normalized, but #{result.dump}"
     end
-  rescue NotImplementedError
   end
-end
+
+  def test_invalid_sequence
+    assert_separately(%w[-r-test-/string/string], <<-'end;')
+      assert_equal("\u{fffd}", Bug::String.new("\xff").normalize_ospath)
+    end;
+  end
+end if Bug::String.method_defined?(:normalize_ospath)