Sam Allardyce had revealed on Thursday that he expected Jaaskelainen to pen his contract by the beginning of next week, and it was confirmed in the wake of the 2-1 defeat by Manchester United that he has done just that.
Jaaskelainen said, "I have been here for nine years now and we have improved all the time."
"Even though we are not yet in the position we were last season, we have still gone forward and the best thing is I still believe there is more to come.
"I honestly do not believe we have achieved what we are capable of yet."
"It has taken a long time but I just wanted to think about everything," said the former VPS Vaasa keeper, who has previously been linked with Manchester United.
"I am happy here and the back-up staff are the best ones to help me get better in my career, which is a very big thing.
"There is no point going somewhere else if they don't have the same back-up.
"Hopefully, I can end my career at Bolton, although I am not really thinking any further than the length of this new contract.
"Obviously, if some big club comes in and wants to buy me it would be a dream but that is all it is.
"The main thing for me now is concentrate on Bolton Wanderers."