Smelted stone not stacking with Silk Touch mined stone

As that title says, I smelted some cobblestone into stone. When I finally got a silktouch pickaxe and mined some stone and went back to store it, it doesn't stack with the stone that I smelted from cobblestone.

This however can be fixed by placing down the smelted stone and mining it again with a silktouch pick, but it time consuming and uses some durability on my pick.