1 files changed, 11 insertions, 0 deletions
diff --git a/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb b/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
index 568e220b15..e9b59f55a7 100644
--- a/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
+++ b/actionpack/test/dispatch/request/url_encoded_params_parsing_test.rb
@@ -126,6 +126,17 @@ class UrlEncodedParamsParsingTest < ActionDispatch::IntegrationTest
     assert_parses expected, query
   end
 
+  test "ambiguous params returns a bad request" do
+    with_routing do |set|
+      set.draw do
+        post ':action', :to => ::UrlEncodedParamsParsingTest::TestController
+      end
+
+      post "/parse", "foo[]=bar&foo[4]=bar"
+      assert_response :bad_request
+    end
+  end
+
   private
     def with_test_routing
       with_routing do |set|