diff --git a/test/ruby/test_m17n.rb b/test/ruby/test_m17n.rb
index db6f3b928d..4cf79d0037 100644
--- a/test/ruby/test_m17n.rb
+++ b/test/ruby/test_m17n.rb
@@ -897,6 +897,9 @@ class TestM17N < Test::Unit::TestCase
     }
     s = e("\xa3\xb0\xa3\xb1\xa3\xb2\xa3\xb3\xa3\xb4")
     assert_equal(e("\xa3\xb0z\xa3\xb2\xa3\xb3\xa3\xb4"), s.gsub(/\xa3\xb1/e, "z"))
+
+    assert_equal(Encoding::EUC_JP, (a("").gsub(//) { e("") }.encoding))
+    assert_equal(Encoding::EUC_JP, (a("a").gsub(/a/) { e("") }.encoding))
   end
 
   def test_end_with