[Question] How to specify a facet for a nullable type?

[GauthierPLM]

I have a type for which I would like to specify that maxLength is 165. However, the type being a nullable string (string | nil), specifying the facet like I did in the example is not authorised (according to Anypoint' Design Center validation).

What is the right way to specify the maxLength?

#%RAML 1.0 DataType
type: object
properties:
  url:
    type: string | nil
    maxLength: 165
    required: false