In Debian, it might be called kernel-headers, but I don't know. If there's a kernel-source that matches the kernel you're running, install it. If not, go for the headers.
Once you've got that, make a symlink from /lib/modules/$(uname -r)/build that points at the base of wherever the kernel source (or headers) went. The idea is to make it so that /lib/modules/$(uname -r)/build/include is the path to the kernel header files (and linux/modversions.h, for instance, is in that include directory).