diff --git a/src/DurableTask.AzureStorage/OrchestrationSessionManager.cs b/src/DurableTask.AzureStorage/OrchestrationSessionManager.cs
index 04b8b19dd..51a6e07ba 100644
--- a/src/DurableTask.AzureStorage/OrchestrationSessionManager.cs
+++ b/src/DurableTask.AzureStorage/OrchestrationSessionManager.cs
@@ -116,7 +116,10 @@ public bool IsControlQueueReceivingMessages(string partitionId)
 
         public bool IsControlQueueProcessingMessages(string partitionId)
         {
-            return this.activeOrchestrationSessions.Values.Where(session => string.Equals(session.ControlQueue.Name, partitionId)).Any();
+            lock (this.messageAndSessionLock)
+            {
+                return this.activeOrchestrationSessions.Values.Where(session => string.Equals(session.ControlQueue.Name, partitionId)).Any();
+            }
         }
 
         async Task DequeueLoop(string partitionId, ControlQueue controlQueue, CancellationToken cancellationToken)