diff --git a/helper/tmpdir-setup b/helper/tmpdir-setup
index 088acdf3..8cf77322 100755
--- a/helper/tmpdir-setup
+++ b/helper/tmpdir-setup
@@ -54,7 +54,7 @@ cmd_cleanup() {
 
     mountpoint=$mntdir/$MXQ_JOBID
 
-    umount $mountpoint
+    umount -l $mountpoint
     rmdir $mountpoint
 }