SqlClient: [SQL Server 2005] System.Data.SqlClient: pre-login fails with SSL error even with Encryption=false

Platform : Debian 8 “Jessie” Runtime : 1.0.0-preview1-002702,coreclr,x64,linux System.Data.SqlClient : 4.1.0-rc2-24027

ConnectionString : Server=tcp:server.domain.lan,1433;User ID=XXXX;Password=XXXX;Encrypt=False"

An attempt to connect to a Microsoft SQL Server 2005 instance results in the following exception:

Project foo (.NETCoreApp,Version=v1.0) was previously compiled. Skipping compilation.
Unhandled Exception: System.Data.SqlClient.SqlException: A connection was successfully established with the server, but then an error occurred during the pre-login handshake. (provider: SSL Provider, error: 31 - Encryption(ssl/tls) handshake failed) ---> System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: size
   at System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size)
   at System.Data.SqlClient.SNI.SslOverTdsStream.Read(Byte[] buffer, Int32 offset, Int32 count)
   at System.IO.Stream.<>c.<BeginReadInternal>b__39_0(Object <arg>)
   at System.Threading.Tasks.Task`1.InnerInvoke()
   at System.Threading.Tasks.Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Threading.Tasks.TaskToApm.End[TResult](IAsyncResult asyncResult)
   at System.Net.FixedSizeReader.ReadCallback(IAsyncResult transportResult)
--- End of stack trace from previous location where exception was thrown ---
   at System.Net.Security.SslState.InternalEndProcessAuthentication(LazyAsyncResult lazyResult)
   at System.Net.Security.SslState.EndProcessAuthentication(IAsyncResult result)
   at System.Threading.Tasks.TaskFactory`1.FromAsyncCoreLogic(IAsyncResult iar, Func`2 endFunction, Action`1 endAction, Task`1 promise, Boolean requiresSynchronization)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Data.SqlClient.SNI.SNITCPHandle.EnableSsl(UInt32 options)
   at System.Data.SqlClient.SNI.SNIProxy.EnableSsl(SNIHandle handle, UInt32 options)
   --- End of inner exception stack trace ---
   at System.Data.SqlClient.SqlInternalConnectionTds..ctor(DbConnectionPoolIdentity identity, SqlConnectionString connectionOptions, Object providerInfo, Boolean redirectedUserInstance, SqlConnectionString userConnectionOptions, SessionData reconnectSessionData, Boolean applyTransientFaultHandling)
   at System.Data.SqlClient.SqlConnectionFactory.CreateConnection(DbConnectionOptions options, DbConnectionPoolKey poolKey, Object poolGroupProviderInfo, DbConnectionPool pool, DbConnection owningConnection, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionFactory.CreatePooledConnection(DbConnectionPool pool, DbConnection owningObject, DbConnectionOptions options, DbConnectionPoolKey poolKey, DbConnectionOptions userOptions)
   at System.Data.ProviderBase.DbConnectionPool.CreateObject(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.UserCreateRequest(DbConnection owningObject, DbConnectionOptions userOptions, DbConnectionInternal oldConnection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, UInt32 waitForMultipleObjectsTimeout, Boolean allowCreate, Boolean onlyOneCheckConnection, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionPool.TryGetConnection(DbConnection owningObject, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionFactory.TryGetConnection(DbConnection owningConnection, TaskCompletionSource`1 retry, DbConnectionOptions userOptions, DbConnectionInternal oldConnection, DbConnectionInternal& connection)
   at System.Data.ProviderBase.DbConnectionInternal.TryOpenConnectionInternal(DbConnection outerConnection, DbConnectionFactory connectionFactory, TaskCompletionSource`1 retry, DbConnectionOptions userOptions)
   at System.Data.SqlClient.SqlConnection.TryOpen(TaskCompletionSource`1 retry)
   at System.Data.SqlClient.SqlConnection.Open()
   at ConsoleApplication.Program.Main(String[] args)

To me, the error looks as if the Encrypt=false just does not get communicated properly in the PRELOGIN packet because the exception is the same no matter if I set Encrypt to true (the default) or false.

Adding TrustServerCertificate=true with the Encrypt setting enabled or disabled has no effect.

The Encrypt setting is parsed as if I specify an invalid value for it, I get an error about it.