diff --git a/railties/test/isolation/abstract_unit.rb b/railties/test/isolation/abstract_unit.rb
index 17c3f979c0..2c4d9c5995 100644
--- a/railties/test/isolation/abstract_unit.rb
+++ b/railties/test/isolation/abstract_unit.rb
@@ -69,7 +69,8 @@ module TestHelpers
 
     def assert_welcome(resp)
       assert_equal 200, resp[0]
-      assert resp[1]["Content-Type"] = "text/html"
+      assert_match 'text/html', resp[1]["Content-Type"]
+      assert_match 'charset=utf-8', resp[1]["Content-Type"]
       assert extract_body(resp).match(/Welcome aboard/)
     end