Getting One SP To Call Other SPs

I've written a T-SQL stored procedure that I want to call other stored procedures.  The opening part of it looks like this:
set ANSI_NULLS ON
set QUOTED_IDENTIFIER ON
GO

ALTER PROCEDURE [dbo].[spArchive]
  @dtArchiveBefore DateTime
AS

EXEC spArchiveAHD @dtArchiveBefore
GO

EXEC spArchiveContract_History @dtArchiveBefore
GO

EXEC spArchiveContracts @dtArchiveBefore
GO

 
But I'm getting this error repeatedly: Msg 137, Level 15, State 2, Line 2  Must declare the scalar variable "@dtArchiveBefore".

I've searched for this term but can't figure out what's wrong with my code.
Any ideas?
Robert W.