Placing block near a sign

What I expected to happen was doing a floor with signs with lava on them.

What actually happened: I put one sign on a block (it was ok), but after I can't place signs/blocks just near to it when I right click on it.

Steps to Reproduce:
1. Place a sign one the face of a block
2. Try do place a other sign or block just in front of this sign by right click on it like we did in the latest version
3. Sorry for my english I'm french