EF6 - Error inserting 2 related objects in a single SaveChanges (no replies)

Hi,

I am attepting to insert two related objects Client and Quote (where Quote has a Client) in a single call to save changes. Code is:

var client = new Client();
db.Client.Add(client);
var quote = new Quote();
quote.Client = client;
db.Quote.Add(quote);

db.SaveChanges();

Exception is:

Additional information: An error occurred while updating the entries. See the inner exception for details.

at System.Data.Entity.Internal.InternalContext.SaveChanges()
at System.Data.Entity.Internal.LazyInternalContext.SaveChanges()
at System.Data.Entity.DbContext.SaveChanges()
at MyTestClass...

Inner Exception is:
{"The specified value is not an instance of a valid constant type.\r\nParameter name: type"}

at System.Data.Entity.Core.Mapping.Update.Internal.UpdateTranslator.Update()
at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.<Update>b__2(UpdateTranslator ut)
at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.Update[T](T noChangesResult, Func`2 updateFunction, Boolean throwOnClosedConnection)
at System.Data.Entity.Core.EntityClient.Internal.EntityAdapter.Update(Boolean throwOnClosedConnection)
at System.Data.Entity.Core.Objects.ObjectContext.<SaveChangesToStore>b__33()
at System.Data.Entity.Core.Objects.ObjectContext.ExecuteInTransaction[T](Func`1 func, IDbExecutionStrategy executionStrategy, Boolean startLocalTransaction, Boolean releaseConnectionOnSuccess)
at System.Data.Entity.Core.Objects.ObjectContext.SaveChangesToStore(SaveOptions options, IDbExecutionStrategy executionStrategy)
at System.Data.Entity.Core.Objects.ObjectContext.<>c__DisplayClass28.<SaveChanges>b__25()
at System.Data.Entity.Infrastructure.DefaultExecutionStrategy.Execute[TResult](Func`1 operation)
at System.Data.Entity.Core.Objects.ObjectContext.SaveChanges(SaveOptions options)
at System.Data.Entity.Internal.InternalContext.SaveChanges()



Entity classes:

public class Client
{
[Key]
public long Id { get; set; }
....
}

public class Quote
{

[Column("id")]
[Key]
public long Id { get; set; }

[Column("client")]
[ForeignKey("Client")]
public long ClientId { get; set; }

public virtual Client Client { get; set; }
...
}


Libraries:
EF6
MySql.Data.dll v6.8.3
MySql.Data.Entity.EF6.dll v6.8.3

If I add a db.SaveChanges() after the db.Client.Add(client) line, it will work ok but I want to use the unit of work pattern on group database calls where possible. Any ideas what could be going wrong?