diff --git a/test/ruby/test_dir_m17n.rb b/test/ruby/test_dir_m17n.rb
index a6c9fcadad..ad18ad753c 100644
--- a/test/ruby/test_dir_m17n.rb
+++ b/test/ruby/test_dir_m17n.rb
@@ -31,6 +31,11 @@ class TestDir_M17N < Test::Unit::TestCase
         ents = Dir.entries(".")
         exit ents.include?(filename)
       EOS
+      assert_ruby_status(%w[-EASCII-8BIT], <<-'EOS', nil, :chdir=>d)
+        filename = "\xA4\xA2"
+        ents = Dir.entries(".")
+        exit ents.include?(filename)
+      EOS
     }
   end
 
@@ -42,6 +47,11 @@ class TestDir_M17N < Test::Unit::TestCase
         ents = Dir.entries(".")
         exit ents.include?(filename)
       EOS
+      assert_ruby_status(%w[-EASCII-8BIT], <<-'EOS', nil, :chdir=>d)
+        filename = "\u3042".force_encoding("ASCII-8BIT")
+        ents = Dir.entries(".")
+        exit ents.include?(filename)
+      EOS
     }
   end