He joined Swindon on a one year deal back in the summer from non league Margate as a reserve 'keeper, but after Brezovan broke his arm back in October Smith has been the main 'keeper and has played well in just about every game since.
He will now stay at Swindon until June 2009.
Meanwhile Petr Brezovan could be back from injury earlier than expected and could be ready to play before the end of the season.