When r.LightPropagationVolume=1, Editor crashes on startup after enabling Forward Shading

I have r.LightPropagationVolume=1 in DefaultEngine.ini for our fork of 4.15, but when checking the box for forward shading, and restarting the editor, it crashes, with an “Assertion failed: Data” message, which is from the assertion on this line. If I remove the line about the light propagation volume, it enables just fine. Anyone seen this before? Thanks!

I confirm, same on UE4.18

Same problem on 4.17

same on 4.19