diff --git a/include/rom.sh b/include/rom.sh
index 2fa8c0f..4b2bc27 100644
--- a/include/rom.sh
+++ b/include/rom.sh
@@ -116,9 +116,10 @@ mkcorebootbin()
 
 add_seabios()
 {
+	[ -n "$seabiosname" ] || seabiosname="fallback/payload"
 	_seabioself="elf/seabios/default/$initmode/bios.bin.elf"
 
-	cbfs "$tmprom" "$_seabioself" "fallback/payload"
+	cbfs "$tmprom" "$_seabioself" "$seabiosname"
 	x_ "$cbfstool" "$tmprom" add-int -i 3000 -n etc/ps2-keyboard-spinup
 
 	_z="2"; [ "$initmode" = "vgarom" ] && _z="0"
@@ -137,7 +138,8 @@ add_seabios()
 
 add_grub()
 {
-	cbfs "$tmprom" "$grubelf" "img/grub2"
+	[ -n "$grubname" ] || grubname="img/grub2"
+	cbfs "$tmprom" "$grubelf" "$grubname"
 	printf "set grub_scan_disk=\"%s\"\n" "$grub_scan_disk" \
 	    > "$TMPDIR/tmpcfg" || $err "$target: !insert scandisk"
 	cbfs "$tmprom" "$TMPDIR/tmpcfg" scan.cfg raw
diff --git a/script/trees b/script/trees
index 5be43dc..e219d64 100755
--- a/script/trees
+++ b/script/trees
@@ -12,7 +12,8 @@ set -u -e
 eval `setvars "" xarch srcdir premake cmakedir xlang mode makeargs elfdir cmd \
     project target target_dir targets xtree _f release bootstrapargs mkhelper \
     autoconfargs listfile autogenargs btype tree rev tree_depend build_depend \
-    defconfig postmake mkhelpercfg dry dest_dir mdir cleanargs`; badhash="n"
+    defconfig postmake mkhelpercfg dry dest_dir mdir cleanargs seabiosname \
+    grubname`; badhash="n"
 
 main()
 {
@@ -112,7 +113,7 @@ configure_project()
 {
 	eval `setvars "" xarch xlang build_depend autoconfargs xtree postmake \
 	    tree_depend makeargs btype mkhelper bootstrapargs premake release \
-	    cleanargs`
+	    cleanargs grubname seabiosname`
 	_tcfg="$1/target.cfg"; badhash="n"; [ -f "$_tcfg" ] || btype="auto"
 	[ -f "$datadir/mkhelper.cfg" ] && eval `setcfg "$datadir/mkhelper.cfg"`