3D Sound not playing in Game Panel

We've recently begun dabbling in 3D sounds, and have encountered a very weird problem.

With this new 3D sound, it can be heard from the Editor's Game panel. Switch back to scene (with the scene still running) and the audio comes through fine. In a full build it works as well.

Has anyone else encountered this? How did you solve it?

Please note that the audio listener can be right on top of the audio source, and there's still nothing in the Game panel.