API can't list files in branches with a / in the name

We're using the API endpoint to list files in a repo at a specific branch:

https://bitbucket.org/!api/1.0/repositories/

/

/directory/

Recently it started acting weird when a branch name containing forward slashes is passed to it. We tried both passing the branch name as is (that returns a 404) or with the branch name url-encoded (that gives us an odd 401):

GET https://bitbucket.org/!api/1.0/repositories/jbpros/cucumber-pro-test/directory/master => 200
GET https://bitbucket.org/!api/1.0/repositories/jbpros/cucumber-pro-test/directory/path-like%2Fbranch%2Fname => 401
GET https://bitbucket.org/!api/1.0/repositories/jbpros/cucumber-pro-test/directory/path-like/branch/name => 404

Is there something we're missing or is there something broken on your end?