diff --git a/services/maintenance/scripts/pi_usb_scratch.sh b/services/maintenance/scripts/pi_usb_scratch.sh
index 5efff529..4c7ebddd 100755
--- a/services/maintenance/scripts/pi_usb_scratch.sh
+++ b/services/maintenance/scripts/pi_usb_scratch.sh
@@ -228,7 +228,7 @@ ensure_tmp_tmpfs_live() {
 
 find_existing_mount_source() {
   local target="$1"
-  host_sh "findmnt -T '${target}' -n -o SOURCE 2>/dev/null || true"
+  host_sh "if mountpoint -q '${target}'; then findmnt -T '${target}' -n -o SOURCE 2>/dev/null || true; fi"
 }
 
 auto_discover_removable_partition() {