Standing in between fire and a powder snow block doesn't melt the powder snow

The Bug:

Even when the player is standing in between a fire block and a powder snow block, the powder snow doesn't disappear.

 

To Reproduce:

1. Place powder snow and light a block on fire right next to the powder snow
2. Go into survival / adventure mode
3. Stand on the powder snow block first
4. Then stand on the fire block half way

Results:

The powder snow block doesn't disappear