Dispencer doesn't create grass + flowers when bone meal is inside

I made flower farms in the past. You put a dispenser upside down put bonemeal in it and press a button. But i havent build one for a long time. And now its not working.

 

What i expected to happened was...:

**Grass and flowers grown

 

What actually happened was...:

****Poof and bonemeal stays in dispencer

 

Steps to Reproduce:
1. Put a dispencer upsidedown with one air block in between 
2. Fill the dispencer with some bonemeal
3. Put a button on the dispencer
4. Press button