Cannot find serializer for text/html

I am trying to use Prism to mock an API. I have the following get request in swagger: 2.0

/some/url:
    get:
      tags:
        - sometag
      summary: SomeSummary
      description: Some description
      operationId: getSomeOperationId
      produces:
        - text/html
      responses:
        '200':
          description: Ok
          schema:
            type: string
            example: <html><head><title>a page</title></head><body><p>a paragraph</p></body></html>

When I attempt a request, the response is the following: {"type":"https://stoplight.io/prism/errors#UNKNOWN","title":"Cannot find serializer for text/html","status":500,"detail":""}

Changing text/html to text/plain does work. However, the result is just the text next to example in a html page instead of the page that I am trying to return and render.

What am I doing wrong?

I run Prism using the stoplight/prism:3 Docker image