diff --git a/xorriso-dd-target/xorriso-dd-target b/xorriso-dd-target/xorriso-dd-target
index 6275dcf7..e054ff1b 100755
--- a/xorriso-dd-target/xorriso-dd-target
+++ b/xorriso-dd-target/xorriso-dd-target
@@ -17,6 +17,7 @@ fi
 # (Listed with increasing priority.)
 lsblk_cmd=
 dd_cmd=
+umount_cmd=
 if test "$(whoami)" = "root"
 then
   sudo_x_dir_list="/usr/bin /bin /usr/sbin /sbin"