diff --git a/test/extra_field_test.rb b/test/extra_field_test.rb
index 6f2ec65b..52140a2d 100644
--- a/test/extra_field_test.rb
+++ b/test/extra_field_test.rb
@@ -35,6 +35,8 @@ def test_ntfs
     assert_equal(t, extra['NTFS'].mtime)
     assert_equal(t, extra['NTFS'].atime)
     assert_equal(t, extra['NTFS'].ctime)
+
+    assert_equal(str.force_encoding('BINARY'), extra.to_local_bin)
   end
 
   def test_merge