diff --git a/tools/mki-build-propagator b/tools/mki-build-propagator
index f8c57df..e4107ac 100755
--- a/tools/mki-build-propagator
+++ b/tools/mki-build-propagator
@@ -33,8 +33,18 @@ printf '%s\n' "${PROPAGATOR_VERSION:-}" > /tmp/.VERSION
 
 rm -f /.image/syslinux/alt0/full.cz
 
-[ ! -f /tmp/modules ] ||
-	cat "\$libdir/propagator/initfs" /tmp/modules > /.image/syslinux/alt0/full.cz
+if [ -f /tmp/modules ]
+then
+	mkdir -p /tmp/initfsroot
+	pushd /tmp/initfsroot
+	(
+	    gzip -dc "\$libdir/propagator/initfs" | cpio -id
+	    gzip -dc /tmp/modules
+	) | cpio -id
+	find | cpio -o | gzip > /.image/syslinux/alt0/full.cz
+	popd
+	rm -rf /tmp/initfsroot
+fi
 
 sed \
 	-e "s,@LIBDIR@,\$libdir," \