diff --git a/doc/docbook.sh b/doc/docbook.sh
index fda4e2d..115bc92 100755
--- a/doc/docbook.sh
+++ b/doc/docbook.sh
@@ -1,6 +1,6 @@
 #!/bin/sh
 #$Id$
-#Copyright (c) 2012-2014 Pierre Pronchery <khorben@defora.org>
+#Copyright (c) 2012-2017 Pierre Pronchery <khorben@defora.org>
 #
 #Redistribution and use in source and binary forms, with or without
 #modification, are permitted provided that the following conditions are met:
@@ -42,7 +42,7 @@ XSLTPROC="xsltproc --nonet --xinclude"
 #debug
 _debug()
 {
-	echo "$@" 1>&2
+	echo "$@" 1>&3
 	"$@"
 }
 
@@ -114,7 +114,7 @@ _usage()
 clean=0
 install=0
 uninstall=0
-while getopts "ciuP:" name; do
+while getopts "ciO:uP:" name; do
 	case "$name" in
 		c)
 			clean=1
@@ -123,6 +123,9 @@ while getopts "ciuP:" name; do
 			uninstall=0
 			install=1
 			;;
+		O)
+			export "${OPTARG%%=*}"="${OPTARG#*=}"
+			;;
 		u)
 			install=0
 			uninstall=1
@@ -137,7 +140,7 @@ while getopts "ciuP:" name; do
 	esac
 done
 shift $((OPTIND - 1))
-if [ $# -eq 0 ]; then
+if [ $# -lt 1 ]; then
 	_usage
 	exit $?
 fi
@@ -151,6 +154,7 @@ fi
 [ -z "$DATADIR" ] && DATADIR="$PREFIX/share"
 [ -z "$MANDIR" ] && MANDIR="$DATADIR/man"
 
+exec 3>&1
 while [ $# -gt 0 ]; do
 	target="$1"
 	shift
@@ -194,7 +198,11 @@ while [ $# -gt 0 ]; do
 	#install
 	if [ "$install" -eq 1 ]; then
 		source="${target#$OBJDIR}"
-		$DEBUG $MKDIR -- "$instdir"			|| exit 2
+		dirname=
+		if [ "${source%/*}" != "$source" ]; then
+			dirname="/${source%/*}"
+		fi
+		$DEBUG $MKDIR -- "$instdir$dirname"		|| exit 2
 		$DEBUG $INSTALL "$target" "$instdir/$source"	|| exit 2
 		continue
 	fi