Can someone tell me what I'm likely missing when I try to make vsftpd (v.2.1.0).

Here's where make is bombing out:

sysdeputil.o: In function `vsf_sysdep_check_auth':
sysdeputil.c:(.text+0xaa4): undefined reference to `crypt'
sysdeputil.c:(.text+0xad1): undefined reference to `crypt'
collect2: ld returned 1 exit status
I looked in sysdeputil.c, and there is a C include of <crypt.h> and a couple of references to a crypt() function. Is this a GCC library that I need to install. If so, which one?