Lambda authorizer for appsync don't get operationName field in event

I have an appsync that i attach a lambda authorization. According to docs the event that gets to the lambda looks like this:

{ "authorizationToken": "ExampleAUTHtoken123123123", "requestContext": { "apiId": "aaaaaa123123123example123", "accountId": "111122223333", "requestId": "f4081827-1111-4444-5555-5cf4695f339f", "queryString": "mutation CreateEvent {...}\n\nquery MyQuery {...}\n", "operationName": "MyQuery", "variables": {} } }

according to : https://aws.amazon.com/blogs/mobile/appsync-lambda-auth/

But what I receive in the lambda don't have the field "operationName" no idea why

Thanks in advance