EF ExecuteStoredCommand with ReturnValue parameter

I'm creating a new application which needs to interface with legacy code :(.

The stored procedure I'm attempting to call uses RETURN for its result. My attempts to execute and consume the return value result in the exception:

InvalidOperationException: When executing a command, parameters must be exclusively database parameters or values.

Changing the stored proc to return the value another way isn't desired, since it either requires updating the legacy app or maintaining a nearly duplicate stored proc.

The legacy stored proc synopsis:

DECLARE @MyID INT
INSERT INTO MyTable ...
SELECT @MyID = IDENTITY()
RETURN @MyID

My Entity Framework / DbContext work, which yields the above InvalidOperationException.

 SqlParameter parm = new SqlParameter() {
    ParameterName = "@MyID",
    Direction = System.Data.ParameterDirection.ReturnValue
 };

 DbContext.Database.ExecuteSqlCommand("EXEC dbo.MyProc", parm);

Looking for any and all solutions which don't require the stored proc to be modified.