diff --git a/src/WebJobs.Extensions.DurableTask/OutOfProcMiddleware.cs b/src/WebJobs.Extensions.DurableTask/OutOfProcMiddleware.cs
index 8ca785998..7ac3e8003 100644
--- a/src/WebJobs.Extensions.DurableTask/OutOfProcMiddleware.cs
+++ b/src/WebJobs.Extensions.DurableTask/OutOfProcMiddleware.cs
@@ -257,8 +257,7 @@ await this.LifeCycleNotificationHelper.OrchestratorFailedAsync(
             else
             {
                 // the function failed for some other reason
-
-                string exceptionDetails = functionResult.Exception.ToString();
+                string exceptionDetails = functionResult.Exception?.ToString();
 
                 this.TraceHelper.FunctionFailed(
                     this.Options.HubName,