Comment 1 for bug 1409539

This should naturally get fixed when 0.64 is released upstream and then packaged for Debian/Ubuntu.

In 0.63 and earlier, there's a complicated manifest system so that any local patches (such as Debian/Ubuntu have) cause 0.63 source to no longer declare itself as 0.63. In 0.64 that will be gone.
http://tartarus.org/~simon-git/gitweb/?p=putty.git;a=commit;h=4d8782e74fed043fdf549718f99494622fe9e79b