Atlassian STASH REST API 401

I am trying to use the Stash REST API to get a list of all open stream requests using the URI https://stash.myserver.com/stash/rest/api/1.0/projects/TEST/repos/testrepo

But I always get 401 Unauthorized with the following content:

{"errors":[{"context":null,"message":"You are not permitted to access this resource","exceptionName":"com.atlassian.stash.exception.AuthorisationException"}]}

      

        
        
        
      

    

I am using HTTP Basic Auth and the user definitely has the proper repository permission. It also works if I open the REST URL in the browser when I am logged in, or when I use the JSESSIONID-Cookie.

Is it possible that I need to enable basic auth in Stash? I couldn't find such an option in the admin settings.