--- a/m4/ax_check_zlib.m4	2012-07-16 23:30:38.000000000 +1000
+++ b/m4/ax_check_zlib.m4	2012-07-17 20:42:48.000000000 +1000
@@ -65,12 +65,12 @@
 # Handle user hints
 #
 [AC_MSG_CHECKING(if zlib is wanted)
+zlib_places="/usr/local /usr /opt/local /sw"
 AC_ARG_WITH(zlib,
 [  --with-zlib=DIR root directory path of zlib installation [defaults to
                     /usr/local or /usr if not found in /usr/local]
   --without-zlib to disable zlib usage completely],
 [if test "$withval" != no ; then
-  zlib_places="/usr/local /usr /opt/local /sw"
   AC_MSG_RESULT(yes)
   if test -d "$withval"
   then
@@ -79,6 +79,7 @@
     AC_MSG_WARN([Sorry, $withval does not exist, checking usual places])
   fi
 else
+  zlib_places=
   AC_MSG_RESULT(no)
 fi],
 [AC_MSG_RESULT(yes)])