A problem with fire and pistons

Let us say we lit fire to a netherrack block and under it there was a piston once the piston is activated the block is moved (as usual)but the fire on it is gone. I am not sure if this is a bug or something intentional but, if it was a bug please try to fix it if not then let it be. I thank you for your time and help.

-Just another minecraftian.
Messedupboy