Akka.Persistence AtLeastOnceDelivery RegAck issue

[Aaronontheweb]

Saw this show up in the build log for an unrelated set of changes - not sure what the issue is here or if it's just a particular spec that is creating this issue:

[15:59:56]  [Step 2/2] [ERROR][9/8/2016 3:59:56 PM][Thread 0004][akka://PersistenceSpec-159/system/deadLetterListener] Unable to cast object of type 'ReqAck' to type 'Akka.Event.DeadLetter'.
[15:59:56]  [Step 2/2] Cause: System.InvalidCastException: Unable to cast object of type 'ReqAck' to type 'Akka.Event.DeadLetter'.
[15:59:56]  [Step 2/2]    at Akka.Event.DeadLetterListener.Receive(Object message) in D:\BuildAgent\work\d26c9d7f36545acd\src\core\Akka\Event\DeadLetterListener.cs:line 38
[15:59:56]  [Step 2/2]    at Akka.Actor.ActorBase.AroundReceive(Receive receive, Object message) in D:\BuildAgent\work\d26c9d7f36545acd\src\core\Akka\Actor\ActorBase.cs:line 154
[15:59:56]  [Step 2/2]    at Akka.Actor.ActorCell.ReceiveMessage(Object message) in D:\BuildAgent\work\d26c9d7f36545acd\src\core\Akka\Actor\ActorCell.DefaultMessages.cs:line 168
[15:59:56]  [Step 2/2]    at Akka.Actor.ActorCell.Invoke(Envelope envelope) in D:\BuildAgent\work\d26c9d7f36545acd\src\core\Akka\Actor\ActorCell.DefaultMessages.cs:line 79