1 files changed, 3 insertions, 0 deletions
diff --git a/actionpack/lib/action_dispatch/testing/assertions/response.rb b/actionpack/lib/action_dispatch/testing/assertions/response.rb
index 93f9fab9c2..68feb26936 100644
--- a/actionpack/lib/action_dispatch/testing/assertions/response.rb
+++ b/actionpack/lib/action_dispatch/testing/assertions/response.rb
@@ -27,6 +27,9 @@ module ActionDispatch
             assert @response.send("#{type}?"), message
           else
             code = Rack::Utils::SYMBOL_TO_STATUS_CODE[type]
+            if code.nil?
+              raise ArgumentError, "Invalid response type :#{type}"
+            end
             assert_equal code, @response.response_code, message
           end
         else