What about libpq-fe.h ?

Hi !

I have small problem with compiling a programm which uses 
libpq-fe.h ($Id: libpq-fe.h,v 1.80 2001/11/08 20:37:52 momjian Exp $) ...
When i wana compile the programm i get the error
'sizeof appliend to an incomplete type' for statement sizeof(PGconn)
so the question is: for the statement 'typedef struct pg_conn PGconn;'
what about the struct pg_conn ? 
how get libpq-fe.h access to struct pg_conn ?
and finally ... how can i fix it ?

mfg,
Antonio