stat.mineBlock.minecraft:grass doesn't work.

Example:
I create 3 types stat.mimeBlock objectives :
Dirt type stat.mimeBlock.minecraft:dirt
Grass type stat.mineBlock.minecraft:grass
Mycelium type stat.mineBlock.minecraft:mycelium

If i mine a dirt block, my Dirt objective win 1. (Normal)
If i mine a grass block, my Dirt objective win 1, but no my Grass objective. (Bug)
If i mine a mycelium block, my Mycelium objective win 1. (Normal)

Tanks