diff --git a/src/orca/default.py b/src/orca/default.py
index decd01a..3c45ddd 100644
--- a/src/orca/default.py
+++ b/src/orca/default.py
@@ -3730,6 +3730,13 @@ class Script(script.Script):
         - event: the Event
         """
 
+        # There seems to be some applications which fire extra
+        # window:activated events (Thunderbird is a prime example)
+        # It seems nonsense that a window could send the event twice
+        # so we should only pay attention to the first.
+        if orca_state.activeWindow == event.source:
+            return
+
         self.windowActivateTime = time.time()
         orca.setLocusOfFocus(event, event.source)
 
