Redhat 6.0 Link Error: Undefined Reference to crypt

I'm trying to compile a program on Redhat 6.0 with the Postgres 6.4 the came
with it.  
I get the following link error:
/usr/lib/libpq.so: Undefined reference to "crypt"
Does postgres need a difference libc or glibc?  Redhat comes with:
libc 5.3.13
glibc 2.1.1

Thanks!

Rob Klein
System Administrator
Ober, Kaler, Grimes and Shriver
120 East Baltimore St
Baltimore, MD 21202