This has been fixed in fish's master branch since 03e0f1eb21e9df76ed792cbd8349d04ec29b8906. You'll want to backport 03e0f1eb21e9df76ed792cbd8349d04ec29b8906, 94b71353ef16e90db850431fa226ff7c33939254 and b3d5fb71f484de4dae8103ab4ac099377b3b698c (i.e. the current state of create_manpath_completions.py, which shouldn't depend on any other changes in what will become 2.6.0) or wait for the next release.