diff --git a/lib/ClusterShell/Task.py b/lib/ClusterShell/Task.py
index ed744f8d..2466b0e3 100644
--- a/lib/ClusterShell/Task.py
+++ b/lib/ClusterShell/Task.py
@@ -950,7 +950,10 @@ def _terminate(self, kill):
         """
         Abort completion subroutine.
         """
-        assert self._quit == True
+        assert self._quit is True
+
+        if self._terminated:
+            return
         self._terminated = True
 
         if kill: