Pistons were light transparent before this snapshot and this is now changed. It breaks some uses of pistons. For example hidden lighting under piston
Some other blocks:
Daylight sensor
Enchantment table
End portal frame
Linked issues
is duplicated by 4
relates to 3
Comments 1
Sysel
Intended. Blocks like slabs, stairs, pistons, and snow layers now use "directional opacity," where certain faces do or do not let light pass.