testforblock on 36 dont found

I can confirm this bug but I also found a solution:
you can use: '/testforblock x y z minecraft:piston_head'.

'36' or 'minecraft:piston_extension' gives me the Error you have, too.

Unable to reproduce.

Is this still a concern in the current Minecraft version 1.7.2 / Launcher version 1.3.4 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.