diff --git a/net_alerter/net_alerter.py b/net_alerter/net_alerter.py
index d9eb169..6f79466 100644
--- a/net_alerter/net_alerter.py
+++ b/net_alerter/net_alerter.py
@@ -151,8 +151,7 @@ def _check_churn(mac: str, ip: str) -> bool:
         events.append(now)
         _churn_tracker[mac] = events
         if len(events) >= CHURN_THRESHOLD:
-            with known_lock:
-                infrastructure_ips.add(ip)
+            infrastructure_ips.add(ip)
             logging.info(f"Churn suppression: {ip} (MAC:{mac}) cycled {len(events)}x in {CHURN_WINDOW_SEC//60}min — auto-added to infrastructure")
             return True
     return False
diff --git a/net_alerter/test_net_alerter.py b/net_alerter/test_net_alerter.py
index 3d4741e..bebd48f 100644
--- a/net_alerter/test_net_alerter.py
+++ b/net_alerter/test_net_alerter.py
@@ -39,6 +39,7 @@ def cleanup_after_each_test():
     net_alerter.departure_timers.clear()
     net_alerter.known_devices.clear()
     net_alerter.last_departed_time.clear()
+    net_alerter._churn_tracker.clear()
     cleanup_flap_state()
     # Force garbage collection to ensure threads are cleaned up
     import gc