diff --git a/defaultenv/bin/boot b/defaultenv/bin/boot
index fa68748..788a781 100644
--- a/defaultenv/bin/boot
+++ b/defaultenv/bin/boot
@@ -34,8 +34,8 @@
 	fi
 
 	if [ x$rootfs_type = xubifs ]; then
-		if [ x$ubiroot = x ]; then
-			ubiroot = "root"
+		if [ -z $ubiroot ]; then
+			ubiroot="root"
 		fi
 		bootargs="$bootargs root=ubi0:$ubiroot ubi.mtd=$rootfs_mtdblock"
 	else