The Kenyan born defender spent last season on work experience at Nene Park and made more first team apperances than any other player.
He is a product of the Raeding Academy after joining as a schoolboy.
Diamonds boss Garry Hill commented "Curtis did extremely well for us last season and I am delighted that we have managed to secure his services for two more years. The squad is taking shape nicely and we are now well into our pre-season training programme so as to ensure that we will be firing on all cylinders come our first league fixture of the season away at Eastbourne Borough on Saturday 9th August 2008".