diff --git a/entry.sh b/entry.sh
index 366552a..78558f3 100755
--- a/entry.sh
+++ b/entry.sh
@@ -27,7 +27,7 @@ fi
 
 
 echo "Setup backup cron job with cron expression BACKUP_CRON: ${BACKUP_CRON}"
-echo "${BACKUP_CRON} /bin/backup >> /var/log/cron.log 2>&1" > /var/spool/cron/crontabs/root
+echo "${BACKUP_CRON} /usr/bin/flock -n /var/run/backup.lock /bin/backup >> /var/log/cron.log 2>&1" > /var/spool/cron/crontabs/root
 
 # Make sure the file exists before we start tail
 touch /var/log/cron.log