diff --git a/ADDITIONS/postfixadmin-mailbox-postcreation.sh b/ADDITIONS/postfixadmin-mailbox-postcreation.sh
index ba779b9f..472606aa 100644
--- a/ADDITIONS/postfixadmin-mailbox-postcreation.sh
+++ b/ADDITIONS/postfixadmin-mailbox-postcreation.sh
@@ -61,7 +61,8 @@ if [ "x${MDM}" = "x" ]; then
     exit 1
 fi
 
-$MDM "$maildir"
+"${MDM}" "${maildir}"
+
 if [ ! -d "$maildir" ]; then
     echo "$0: maildirmake didn't produce a directory; bailing out."
     exit 1