Put the summary of the bug you're having here

What I expected to happen was...:
The water to stop flowing.

What actually happened was...:
The top water (source) block stopped when i placed a block on it and the non-source block of water was still there and there the water was still flowing

Steps to Reproduce:
1. Place a watersorce (water bukket)
2. Place a sign to stop the water sorce
3. The water stays