Smith cannot play against Norwich on Saturday because his loan from Chelsea has now expired.
An extension until the end of the season, which was agreed some time ago, counts as a separate loan deal and starts from the beginning of January.
But both Smith and Timoska must sit out the New Year's Day clash with Colchester as the Football League offices are still closed because of the festive period - meaning signings will not be registered until January 2.
Finnish defender Timoska, 26, agreed a move from MyPa-47 several weeks ago but cannot play for his new club until the transfer window opens.