diff --git a/lib/romlib/gentbl.sh b/lib/romlib/gentbl.sh
index 0695f6e..e64cfe2 100755
--- a/lib/romlib/gentbl.sh
+++ b/lib/romlib/gentbl.sh
@@ -6,6 +6,7 @@
 set -e
 
 output=jmptbl.s
+build=.
 
 for i
 do
@@ -14,27 +15,45 @@
 		output=$2
 		shift 2
 		;;
+	-b)
+		build=$2
+		shift 2
+		;;
 	--)
 		shift
 		break
 		;;
 	-*)
-		echo usage: gentbl.sh [-o output]  file ... >&2
+		echo usage: gentbl.sh [-o output] [-b dir] file ... >&2
 		exit 1
 		;;
 	esac
 done
 
 tmp=`mktemp`
-trap "rm -f $tmp" EXIT INT QUIT
-
+trap "rm -f $$.tmp" EXIT INT QUIT
 rm -f $output
 
+# Pre-process include files
+awk '!/^$/ && !/[:blank:]*#.*/{
+if (NF == 2 && $1 == "include") {
+	while ((getline line < $2) > 0)
+		if (line !~ /^$/ && line !~ /[:blank:]*#.*/)
+			print line
+		close($2)
+} else
+	print
+}' "$@" |
+awk -v OFS="\t" '
+BEGIN{print "#index\tlib\tfunction\t[patch]"}
+{print NR-1, $0}' | tee $build/jmptbl.i |
 awk -v OFS="\n" '
 BEGIN {print "\t.text",
              "\t.globl\tjmptbl",
              "jmptbl:"}
       {sub(/[:blank:]*#.*/,"")}
-!/^$/ {print "\tb\t" $3}' "$@" > $tmp
-
-mv $tmp $output
+!/^$/ {if ($3 == "reserved")
+		print "\t.word\t0x0"
+	else
+		print "\tb\t" $3}' > $$.tmp &&
+mv $$.tmp $output