The 20-year-old impressed in two pre-season freindlies, prompting manager Jason Tindall to offer him a full-time contract.
"Justin played against AFC Bournemouth and Ringwood Town and he has been doing very well," Tindall told the Dorset Echo.
"He works hard, is very strong and is also comfortable on the ball so we are delighted he is going to sign.
"He was at Nottingham Forest last year where he spent most of the season in the reserves and there is no doubt that he will strengthen us."
Source: http://www.confguide.com/newsArticle.do?id=6852