Piston head does not render while the piston extends after breaking an unpushable block

Upon powering a piston which is facing an unpushable block such as obsidian, and then breaking said block, the piston head will not render until it is fully extended.

I also managed to capture a screenshot with only the outline of the piston head rendering; I assume this was the moment that block 36 was replaced by the full piston head block.