Structure Block place a piston without head

The Bug:

Structure Blocks can place a piston without a piston head. 

Steps to Reproduce:

1. Save a structure template like save.png below.

2. Place a Structure Block and load the template.You can see a piston with head.

3. Load the template again.

Observed Behavior:

The piston lost it's piston head.

Expected Behavior:

The piston has piston head.