diff --git a/restic-backup.sh b/restic-backup.sh
index 0741497..1549d25 100755
--- a/restic-backup.sh
+++ b/restic-backup.sh
@@ -149,6 +149,10 @@ fi  # stage dumps
 
 if [ "$STAGE" = all ] || [ "$STAGE" = backup ]; then
 
+# clear locks left by a killed run (safe: only stale ones are removed);
+# otherwise a single interrupted backup blocks forget/prune for ever
+$RESTIC -r "$REPO" unlock >/dev/null 2>&1 || true
+
 log "restic backup -> $REPO"
 $RESTIC -r "$REPO" backup \
     --pack-size 64 --read-concurrency 8 -o s3.connections=8 \