diff --git a/src/ZB.MOM.WW.ScadaBridge.Communication/Actors/SiteAlarmAggregatorActor.cs b/src/ZB.MOM.WW.ScadaBridge.Communication/Actors/SiteAlarmAggregatorActor.cs
index 22ef5b05..a8007097 100644
--- a/src/ZB.MOM.WW.ScadaBridge.Communication/Actors/SiteAlarmAggregatorActor.cs
+++ b/src/ZB.MOM.WW.ScadaBridge.Communication/Actors/SiteAlarmAggregatorActor.cs
@@ -568,7 +568,9 @@ public sealed class SiteAlarmAggregatorActor : ReceiveActor, IWithTimers
         // A down stream is reopened in preference to fanning out: the reopen's connect
         // callback seeds by itself, so doing both would double the work.
         var reopening = false;
-        if (_streamDown && !_openInFlight)
+        // Not while a backoff reconnect is already scheduled: the tick used to open a stream
+        // and the pending ReconnectAlarmStream then opened a second one (a double subscribe).
+        if (_streamDown && !_openInFlight && !Timers.IsTimerActive(ReconnectTimerKey))
         {
             _log.Info("Site-alarm gRPC stream for {0} was down; reopening on reconcile tick", _siteIdentifier);
             if (_retryBudgetExhausted)