tsearch2 in 7.4beta1 compile problem

After installing PostgreSQL 7.4 beta 1 from source, I decided to install the
/contrib module tsearch2.

I cd to the tsearch2 directory and typed "make", however I get an error that
yy_current_buffer is an undeclared identifier in wordparser/parser.c (which
is apparently autogenerated with flex from parser.l).

I looked online, and it seemed like I was building the module in the right
way. I also downloaded the latest development version, and that seemed to
fail in the same way.

Has anyone else had this problem? I'm using flex 2.5.31 and gcc 3.3.1.

Thanks,
    Jeff