diff --git a/workers/worker.py b/workers/worker.py
index 03066dc6e..1442195ce 100644
--- a/workers/worker.py
+++ b/workers/worker.py
@@ -171,9 +171,11 @@ class Worker(object):
 
     self._sched.start()
     self._sched.add_job(self.poll_queue, 'interval', seconds=self._poll_period_seconds,
-                        start_date=soon)
-    self._sched.add_job(self.update_queue_metrics, 'interval', seconds=60, start_date=soon)
-    self._sched.add_job(self.run_watchdog, 'interval', seconds=self._watchdog_period_seconds)
+                        start_date=soon, max_instances=1)
+    self._sched.add_job(self.update_queue_metrics, 'interval', seconds=60, start_date=soon,
+                        max_instances=1)
+    self._sched.add_job(self.run_watchdog, 'interval', seconds=self._watchdog_period_seconds,
+                        max_instances=1)
 
     signal.signal(signal.SIGTERM, self.terminate)
     signal.signal(signal.SIGINT, self.terminate)