8.0.1 in a non-standard location and tsearch2

I'm trying to install tsearch2 into an empty database on a new 8.0.1
postgres install. The machine already has an older 7.4 install of
postgres on it, so I gave configure a --prefix=/usr/local/pg801 option.
Postgres installed and started fine (after changing the port), and I
was able to create my new empty database without issues.

Now comes the part where I fail to install tsearch2. I go to the
contrib/tsearch2 directory, run make and make install without issues.
make installcheck tries to connect to the older postgres install (I
don't see an option to set the port it attempts to use), so I try to
pipe tsearch2.sql into the new database. It starts working fine, and
then says:

ERROR: could not find function "tsvector_cmp" in file
"/usr/local/pgsql/lib/tsearch2.so"

.... which is interesting, because it's not trying to use
/usr/local/pg801/ like it's supposed to.

Thoughts?