gmusicbrowser doesn't seem to recognize opus files. Is there anything I can do to make it work?

I understand that my gstreamer install on Ubuntu 16.04 can play opus files, and I can actually play them in VLC, SMplayer, mpv, Rythmbox, etc.

I also thought that gmusicbrowser should be able to play anything that gstreamer understands. (I have "gstreamer 1.x" selected in Settings/ Audio)

I have tried wrapping the opus files in .opus, .ogg, .webm and .mka, but gmusicbrowser never seems to recognize them as audio files.

Thanks for any help