diff --git a/test/ruby/test_dir_m17n.rb b/test/ruby/test_dir_m17n.rb
index 325b1571c9..a72598b360 100644
--- a/test/ruby/test_dir_m17n.rb
+++ b/test/ruby/test_dir_m17n.rb
@@ -307,11 +307,13 @@ class TestDir_M17N < Test::Unit::TestCase
     with_tmpdir do |d|
       names = %W"\u{391 392 393 394 395} \u{3042 3044 3046 3048 304a}"
       names.each do |dir|
-        Dir.mkdir(dir) rescue next
-        begin
-          yield(dir)
-        ensure
-          File.chmod(0700, dir)
+        EnvUtil.with_default_external(Encoding::UTF_8) do
+          Dir.mkdir(dir) rescue next
+          begin
+            yield(dir)
+          ensure
+            File.chmod(0700, dir)
+          end
         end
       end
     end
@@ -321,6 +323,7 @@ class TestDir_M17N < Test::Unit::TestCase
     with_enc_path do |dir|
       open("#{dir}/x", "w") {}
       File.chmod(0300, dir)
+      next if File.readable?(dir)
       assert_warning(/#{dir}/) do
         Dir.glob("#{dir}/*")
       end
@@ -331,6 +334,7 @@ class TestDir_M17N < Test::Unit::TestCase
     with_enc_path do |dir|
       open("#{dir}/x", "w") {}
       File.chmod(0000, dir)
+      next if File.readable?(dir)
       assert_warning(/#{dir}/) do
         Dir.glob("#{dir}/x")
       end
@@ -341,6 +345,7 @@ class TestDir_M17N < Test::Unit::TestCase
     with_enc_path do |dir|
       Dir.mkdir("#{dir}/x")
       File.chmod(0000, dir)
+      next if File.readable?(dir)
       assert_warning(/#{dir}/) do
         Dir.glob("#{dir}/x/")
       end