diff --git a/src/Proto.Actor/Context/ActorContext.cs b/src/Proto.Actor/Context/ActorContext.cs
index b91f4f5b74..09feaabe23 100644
--- a/src/Proto.Actor/Context/ActorContext.cs
+++ b/src/Proto.Actor/Context/ActorContext.cs
@@ -397,7 +397,7 @@ public Task InvokeSystemMessageAsync(SystemMessage msg)
                 Unwatch uw                      => HandleUnwatch(uw),
                 Failure f                       => HandleFailureAsync(f),
                 Restart                         => HandleRestartAsync(),
-                SuspendMailbox or ResumeMailbox => default,
+                SuspendMailbox or ResumeMailbox => Task.CompletedTask,
                 Continuation cont               => HandleContinuation(cont),
                 ProcessDiagnosticsRequest pdr   => HandleProcessDiagnosticsRequest(pdr),
                 ReceiveTimeout _                => HandleReceiveTimeout(),