The 21 year old scored once in 13 games for County at the end of 2015.
He goes back to Rodney Parade until the end of the season.
O'Sullivan has made three previous appearances for City coming off the bench in cup competitions in previous seasons.
The 21 year old scored once in 13 games for County at the end of 2015.
He goes back to Rodney Parade until the end of the season.
O'Sullivan has made three previous appearances for City coming off the bench in cup competitions in previous seasons.