Problem with double halfslabs

I thought that when I put two sandstone slabs on top of each other it would make a sandstone block.

What I expected to happen was I thought that when I put two sandstone slabs on top of each other it would make a sandstone block.

What actually happened was it made a very strange block that looked like two stone halfslabs as a solid block with no line texture in the middle this also happened when i put two stone slabs on top of each other

Steps to Reproduce:
1. Simply put two sandstone half-slabs or stone half-slabs on top of each other.