diff --git a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
index 642c7183cc7a39a1c70fee6a318da284c953b7aa..b55c937e0c4d8fdb7e20752c765ab6273acb6b5f 100644
--- a/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
+++ b/actionpack/lib/action_dispatch/middleware/debug_exceptions.rb
@@ -111,7 +111,7 @@ def render_for_api_application(request, wrapper)
         format = content_type
       else
         formatted_body = body.to_json
-        format = Mime::JSON
+        format = Mime[:json]
       end
 
       render(wrapper.status_code, formatted_body, format)