diff --git a/python/adapters/brcm_openomci_onu/heartbeat.py b/python/adapters/brcm_openomci_onu/heartbeat.py
index 4a7ab1f..5242caa 100644
--- a/python/adapters/brcm_openomci_onu/heartbeat.py
+++ b/python/adapters/brcm_openomci_onu/heartbeat.py
@@ -49,7 +49,7 @@
         self._defer = reactor.callLater(delay, self.check_pulse)
 
     def _stop(self):
-        d, self._defeered = self._defeered, None
+        d, self._defer = self._defer, None
         if d is not None and not d.called():
             d.cancel()