diff --git a/xorriso-dd-target/xorriso-dd-target b/xorriso-dd-target/xorriso-dd-target
index 983dc5e6..4b20a983 100755
--- a/xorriso-dd-target/xorriso-dd-target
+++ b/xorriso-dd-target/xorriso-dd-target
@@ -651,6 +651,7 @@ xdt_list_mounted_of() {
 }
 
 ## Unmount xdt_mounted_devs (maybe filled by xdt_list_mounted_of)
+## $1 : base device name
 xdt_unmount() {
   if test -z "$xdt_mounted_devs"
   then
@@ -674,7 +675,7 @@ xdt_unmount() {
   # Check again if any mount points still exist
   if test -z "$xdt_dummy_run"
   then
-    xdt_list_mounted_of "$2"
+    xdt_list_mounted_of "$1"
     if test -n "$xdt_mounted_devs"
     then
       echo "FAILURE: $xdt_sudo_cmd $xdt_umount_cmd could not remove all mounts: $xdt_mounted_devs" >&2
@@ -685,6 +686,8 @@ xdt_unmount() {
 }
 
 ## Does the work of unmounting and dd-ing
+## $1 : image file path
+## $2 : base device name
 xdt_write_image() {
 
   if test -z "$xdt_umount_cmd"
@@ -705,7 +708,7 @@ xdt_write_image() {
     echo "Would do if not -dummy:"
   fi
 
-  xdt_unmount || return "$?"
+  xdt_unmount "$2" || return "$?"
 
   if test -z "$xdt_dd_cmd"
   then