Upsert against SPOCK server throws MissingKeyException

.NET 2.4.8 against SPOCK (5.0.0-3217, which is Beta2) throws MissingKeyException on Upsert operation.

Here is the call stack

Couchbase.NetClient.dll!Couchbase.IO.Operations.OperationBase.OperationBase(string key, Couchbase.Core.IVBucket vBucket, Couchbase.Core.Transcoders.ITypeTranscoder transcoder, uint opaque, uint timeout) Line 37 C#
Couchbase.NetClient.dll!Couchbase.IO.Operations.OperationBase.OperationBase(string key, Couchbase.Core.IVBucket vBucket, Couchbase.Core.Transcoders.ITypeTranscoder transcoder, uint timeout) Line 53 C#
Couchbase.NetClient.dll!Couchbase.IO.Operations.Authentication.SelectBucket.SelectBucket(string key, Couchbase.Core.Transcoders.ITypeTranscoder transcoder, uint timeout) Line 8 C#
Couchbase.NetClient.dll!Couchbase.IO.ConnectionPoolBase<Couchbase.IO.MultiplexingConnection>.EnableEnhancedAuthentication(Couchbase.IO.IConnection connection) Line 157 C#
> Couchbase.NetClient.dll!Couchbase.IO.SharedConnectionPool<Couchbase.IO.MultiplexingConnection>.Acquire() Line 74 C#
Couchbase.NetClient.dll!Couchbase.IO.Services.PooledIOService.Execute<string>(Couchbase.IO.Operations.IOperation<string> operation) Line 153 C#
Couchbase.NetClient.dll!Couchbase.Core.Server.Send<string>(Couchbase.IO.Operations.IOperation<string> operation) Line 570 C#
Couchbase.NetClient.dll!Couchbase.Core.Buckets.CouchbaseRequestExecuter.SendWithRetry<string>(Couchbase.IO.Operations.IOperation<string> operation) Line 740 C#
Couchbase.NetClient.dll!Couchbase.CouchbaseBucket.Upsert<string>(string key, string value) Line 2969 C#
Sdkd.dll!Sdkd.Commands.SetCommand.ExecuteSingeSync.AnonymousMethod__0() Line 83 C#

Also attaching the client log