diff --git a/doc/scripts/subst.sh b/doc/scripts/subst.sh
index 64bed54..633705a 100755
--- a/doc/scripts/subst.sh
+++ b/doc/scripts/subst.sh
@@ -28,6 +28,8 @@
 PREFIX="/usr/local"
 BINDIR=
 DATADIR=
+INCLUDEDIR=
+LDSO=
 LIBDIR=
 LIBEXECDIR=
 MANDIR=
@@ -35,6 +37,17 @@ SYSCONFDIR=
 [ -f "../config.sh" ] && . "../config.sh"
 [ -z "$BINDIR" ] && BINDIR="$PREFIX/bin"
 [ -z "$DATADIR" ] && DATADIR="$PREFIX/share"
+[ -z "$INCLUDEDIR" ] && INCLUDEDIR="$PREFIX/include"
+if [ -z "$LDSO" ]; then
+	case "$(uname -s)" in
+		Linux)
+			LDSO="/lib/ld-linux-$(uname -p).so.2"
+			;;
+		*)
+			LDSO="/libexec/ld.elf_so"
+			;;
+	esac
+fi
 [ -z "$LIBDIR" ] && LIBDIR="$PREFIX/lib"
 [ -z "$LIBEXECDIR" ] && LIBEXECDIR="$PREFIX/libexec"
 [ -z "$MANDIR" ] && MANDIR="$DATADIR/man"
@@ -148,6 +161,8 @@ while [ $# -gt 0 ]; do
 		-e "s,@PREFIX@,$PREFIX," \
 		-e "s,@BINDIR@,$BINDIR," \
 		-e "s,@DATADIR@,$DATADIR," \
+		-e "s,@INCLUDEDIR@,$INCLUDEDIR," \
+		-e "s,@LDSO@,$LDSO," \
 		-e "s,@LIBDIR@,$LIBDIR," \
 		-e "s,@LIBEXECDIR@,$LIBEXECDIR," \
 		-e "s,@MANDIR@,$MANDIR," \