error linking with PostgreSQL

Here is the code:
#include "libpq-fe.h"

#ifndef HDBUTIL
#define HDBUTIL

class DBConn
{
  public:
    PGconn pg_conn;
    bool Connect();
    bool Disconnect();
};

#endif


... and here is the make error:

tux tb # make
g++  -Wall -g -o0 -lpq -I/usr/include/postgresql/libpq-4 server.cpp
db_util.cpp player.cpp  -o tbserver.exe -L/usr/lib64 `wx-config --
cxxflags` `wx-config --libs`
In file included from server.h:10,
                 from server.cpp:24:
db_util.h:11: error: field 'pg_conn' has incomplete type