Receiving violation: ____ must match pattern: error from validator when running prism

[williamj20]

I'm currently running prism with an openapi spec using the command prism mock test.yaml. Then I'm testing an api response using Postman. I have a parameter defined as:

type: string
pattern: '^[0-9]{32}$'

which should be in the response body of one of my GET requests. However, when I run the GET request on postman, I receive an error like so:

error Violation: response.body.string must match pattern '^[0-9]{32}$'

I thought Prism was supposed to generate this response based on this pattern? Am I misunderstanding/doing something wrong?