Bubbleblock on Soulsand with dispenser

I have a water bucket in a dispenser by some soul sand for a netherwort farm.

Everything works as before, but right in front of the dispenser, there is a bubbleblock space where I can't replant netherwort.

There is still a bubble animation, and the player character bounces, but no water is visible. The blcok right next to that (2 from dispenser) behaves normally.