Audio not working through headphones in editor

As the title says my audio is not coming through my headphones in the editor. Sound plays through the speakers in the editor and works through both the speakers and the headphones in builds.

I'm using Unity 5.3.5f1. I'm developing for Windows and Mac. I'm using what I believe to be a standard sound set up with audio listeners and mixers.

Don't hesitate to ask if more information would help diagnose this problem.