-xml2dir=yes
-AC_ARG_WITH(xml2, [ --with-xml2[=PREFIX] use libxml2 in PREFIX],[xml2dir=$withval])
-if test "$xml2dir" = "yes"; then
+xml2dir=default
+AC_ARG_WITH(xml2, [ --with-xml2[=PREFIX] use libxml2 in PREFIX],[xml2dir=$withval])
+if test "$xml2dir" = "yes" -o "$xml2dir" = "default"; then