PAM module unknown

Hi, I can compile the FreeRADIUS PAM module without any errors. But when I try to use it I always get a module unknown error. For example: AUTH-PAM: BACKGROUND: user 'john' failed to authenticate: Module is unknown This is how I compiled the module: gcc -fPIC -c pam_radius_auth.c gcc -shared -o pam_radius_auth.so pam_radius_auth.o -lpam What did I do wrong?