--- xmlto.in.orig	2011-11-29 03:49:57.000000000 -0800
+++ xmlto.in	2013-01-31 12:47:51.000000000 -0800
@@ -121,6 +121,9 @@ prefix=@prefix@
 # This can be over-ridden, but really we should detect the source
 # document type without needing any help.
 : ${SOURCE_FORMAT=docbook}
+# use MacPorts' XML catalog if XML_CATALOG_FILES not set
+: ${XML_CATALOG_FILES=${prefix}/etc/xml/catalog}
+export XML_CATALOG_FILES
 
 # Get absolute pathnames for FORMAT_DIR and OUTPUT_DIR.
 WD="$(pwd)"