Selection tool is invisible when drawing

I think I might have somehow enabled a thing that makes my selection tool invisible while drawing the selection. Does anyone know how to fix this?
The selection is visible AFTER drawing it but not when selecting.

Welcome @Brin! I think you are experiencing a bug that appears in indexed images when the first palette entry is completely transparent:


We’ve to fix this for v1.2.26 (and v1.3) soon.