diff --git a/test/integration/api_test/authentication_test.rb b/test/integration/api_test/authentication_test.rb
index 5ec6a8824..16c589d3e 100644
--- a/test/integration/api_test/authentication_test.rb
+++ b/test/integration/api_test/authentication_test.rb
@@ -41,8 +41,13 @@ class Redmine::ApiTest::AuthenticationTest < Redmine::ApiTest::Base
   end
 
   def test_invalid_utf8_credentials_should_not_trigger_an_error
+    invalid_utf8 = "\x82"
+    if invalid_utf8.respond_to?(:force_encoding)
+      invalid_utf8.force_encoding('UTF-8') 
+      assert !invalid_utf8.valid_encoding?
+    end
     assert_nothing_raised do
-      get '/users/current.xml', {}, credentials("\x82", "foo")
+      get '/users/current.xml', {}, credentials(invalid_utf8, "foo")
     end
   end