diff --git a/test/test-mail.rb b/test/test-mail.rb
index 4fce98f..bcc4cd5 100644
--- a/test/test-mail.rb
+++ b/test/test-mail.rb
@@ -176,9 +176,11 @@ def decompose
 
     sub_test_case("nested message/rfc822") do
       def test_body
+        uri = fixture_path("nested-rfc822.eml") + "#0-0-0"
+        uri = uri.downcase if Gem.win_platform?
         assert_equal([
                        [
-                         fixture_path("nested-rfc822.eml") + "#0-0-0",
+                         uri,
                          "Sub World",
                        ],
                      ],