The file Yoram is referring to is conf/mount/mount_linux.c in the relevant line linux_version_code(void). Its location in the debian sources is 240 and 265 in the upstream git (as the debian snapshot is seems quite old).
During the build the file is renamed to mountutil.c (no idea why, but it's by upstream design). Anyway, notice the problem is relevant with kernels from Debian testing, unstable, and also stable-backports which has the 3.X scheme instead of 3.x.y Kaplan
