Bug in Api Gateway Authorizer schema for authorizer.type = CUSTOM?

For a while we’ve used a setup where multiple serverless files use the same Api Gateway and share authorizers that are defined in a separate cloudformation stack. We’ve used authorizer type = “CUSTOM” and an authorizerId to point to an existing authorizer, but upon upgrading to serverless v2 I get an error saying: Configuration warning at 'functions.get.events[0].http.authorizer.type': unsupported configuration format

A typical template looks like this:

service: my-test-service
provider:
  name: aws
  region: eu-west-1
  stage: prod
  runtime: python3.7
  apiGateway:
    restApiId: fjei400f
    restApiRootResourceId: af4i4i

functions:
  get:
    handler: handler.handle_stuff
    events:
      - http:
          path: my-path
          method: get
          authorizer:
            type: CUSTOM
            authorizerId: aliwjefij3

But it works just as expected. Is there a bug in the schema definition for the api gateway authorizer setup?

Here is the corresponding Cloudformation docs that confirm that CUSTOM is the right type: