Scaffolding as fuel burns too long

One piece of scaffolding used as fuel in a furnace burns for 60 seconds, 4 times as long as a solid wood block. As it's made from 6 bamboo, which only burns 2.5 seconds, scaffolding should burn for 15 seconds, the same as a wood block.

Steps to reproduce:

1. Place a furnace.
2. Put 1 block of scaffolding in the fuel slot.
3. Put a stack of cobblestone in the input slot.
4. Wait for the fuel to be exhausted.

Expected results:
The furnace smelts 1 cobblestone to stone. Halfway through smelting a second one, the fire goes out.

Actual results:
The furnace smelts 6 cobblestone to stone.