TNT Not Place able on-top of other TNT

TNT Not Place able on-top of other TNT

*What I expected to happen was... The TNT to place on top other TNT *

What actually happened was... I was placing TNT and i could not place it
Describe what happened here

Steps to Reproduce:
1. Place TNT #1
2. Try to place TNT #2 On top
3. ...