RBAC Tests failing on 6.6 server

Some RBAC tests (that make use of the bindGroup() function) are erroring when trying to create the role in pre-7.0 server versions:

unexpected status code: request failed PUT http://test-couchbase-85jh2-0000.test-couchbase-85jh2.test-2cbnd.svc:8091/settings/rbac/groups/bucket-role 400 Bad Request: {\"errors\":{\"roles\":\"Cannot assign roles to user because the following roles are unknown, malformed or role parameters are undefined: [data_reader]\"}} 

This is happening in all tests that make use of the function, for example TestRBACWithBucketScopedRolePre7.

The same test passes in post-7.0, so I suspect that the ScopeRoleSpec or CollectionRoleSpec are being passed on and creating a malformed request in the eyes of 6.6.x (which does not understand collections or scopes.)