Lava with water not making cobble with seegrass.

When lava is placed on the water where there is seagrass it does not break the water block and place a stone block.

What I expected to happen was...:
When there are water and lava in collision there should be a cobble that spawns.

What actually happened was...:
Nothing happened.The lava did nothing.

Steps to Reproduce:
1. Set a 2 water high pool
2. Put seagrass where you want to do the bug
3. Use bone meal on the seagrass to make it 2 block
4. Put lava on top of it