Cobblestone Double Slab has got the texture of a Stone Double Slab

When placing two cobblestone slabs ontop of eachother, it should create a cobblestone double slab. Instead, it has the texture of a double stone slab. This is only the texture though, when breaking a cobblestone double slab it still drops two cobblestone half slabs.

EDIT: It occurs at every slab except wooden ones.