diff --git a/server/home/media-backup b/server/home/media-backup
index d6bf013..79e0596 100755
--- a/server/home/media-backup
+++ b/server/home/media-backup
@@ -81,13 +81,25 @@ mkdir -p "$DEST"
 
 # A borg run holds this lock for 2-4 hours and rewrites index/hints/integrity at the END.
 # Copying mid-run pairs new data chunks with a stale index: a repo that looks fine and
-# fails at restore. Defer rather than queue -- the next weekly run will catch it.
+# fails at restore. AIO's borg runs daily from 07:30 UTC for about 2 hours, so it can
+# still be going when the timer fires. Wait for it to finish, checking every
+# BORG_WAIT_INTERVAL, and defer only if it is still held after BORG_WAIT_MAX. The unit's
+# TimeoutStartSec=24h covers the wait plus the ~50 min sync.
+BORG_WAIT_INTERVAL=300      # 5 min
+BORG_WAIT_MAX=21600         # 6 h
+waited=0
+while [ -e "$BORG_LOCK" ] && [ "$waited" -lt "$BORG_WAIT_MAX" ]; do
+    log "borg is mid-run (lock held at $BORG_LOCK). Waited $((waited / 60)) of $((BORG_WAIT_MAX / 60)) min, checking again in $((BORG_WAIT_INTERVAL / 60)) min"
+    sleep "$BORG_WAIT_INTERVAL"
+    waited=$(( waited + BORG_WAIT_INTERVAL ))
+done
 if [ -e "$BORG_LOCK" ]; then
     log "borg is mid-run (lock held at $BORG_LOCK)"
     log "DEFERRING this week's run rather than copying a torn repo. Next fire: next Saturday."
     log "=== media-backup deferred ==="
     exit 0
 fi
+[ "$waited" -gt 0 ] && log "borg lock released after waiting $((waited / 60)) min, continuing"
 
 avail_gb=$(zfs get -Hp -o value available "$POOL" 2>/dev/null)
 avail_gb=$(( ${avail_gb:-0} / 1024 / 1024 / 1024 ))
diff --git a/server/home/systemd/media-backup.timer b/server/home/systemd/media-backup.timer
index cc5d05a..5875c64 100644
--- a/server/home/systemd/media-backup.timer
+++ b/server/home/systemd/media-backup.timer
@@ -6,8 +6,9 @@ Description=Weekly Media -> Backup pool copy
 # timeshift (04:00), arr-queue-reconcile (04:31), and both ~/Server backups (01:00, 02:00).
 # Saturday specifically because Monday carries the Media scrub and Sunday has
 # raid-check (01:00), docker-prune (05:33) and dind-prune (06:03).
-# gib also runs Nextcloud's borg by hand roughly monthly and is, in his words,
-# not going to be doing that at 5 AM on a Saturday -- so the borg lock should be free.
+# Nextcloud AIO's borg runs daily from 07:30 UTC for about 2 hours, so its lock can
+# overlap this fire. The script waits up to 6 h for the lock, checking every 5 min,
+# and defers the week only if borg is still running after that.
 OnCalendar=Sat *-*-* 05:00:00
 RandomizedDelaySec=15m
 Persistent=true