So, I'm trying to build 0.36pre38 . It fails when it is trying to build arlad/adir.c because it can't find des.h . I have kth-krb4 built from source, which provides /usr/athena/include/des.h , and openssl-dev 0.9.7c-5 from debian, which provides /usr/include/openssl/des.h Which one of these should it be using? Why isn't it finding it?