--- Makefile.orig	2008-10-13 11:25:21.000000000 +0200
+++ Makefile	2008-10-13 11:26:08.000000000 +0200
@@ -59,7 +59,7 @@
 HTML=/html
 BIN=/usr/bin
 MAN=/usr/share/man/man1
-DOC=/usr/share/doc/lisaac
+DOC=${DOC:=/usr/share/doc/lisaac}
 DESTDIR=
 CC=gcc
 CFLAGS=-O2