Stored Procedure returns incorrect scalar value of -1, instead of return value

I am trying to return a scalar value from a stored procedure. I actually want to return the ID of a newly created record, but I have simplified my problem down to a stored procedure that takes an int and attempts to return that same int. This always returns -1. Thank you very much for your help.

Web API Controller call

var idtest = dbconn.my_return_int(123);

The stored procedure:

ALTER PROCEDURE [dbo].[my_return_int]  
    @ID int  
AS  
BEGIN  
    SET NOCOUNT ON;  
    DECLARE @return as int

    SET @return = -999

RETURN @return
END   

The Context generated stored procedure call

public virtual int my_return_int(Nullable<int> iD)  
{  
    var iDParameter = iD.HasValue ?
        new ObjectParameter("ID", iD) :
        new ObjectParameter("ID", typeof(int));

    return (IObjectContextAdapter)this).ObjectContext.ExecuteFunction("my_return_int", iDParameter);  
}