The former Hearts stopper was snapped up at the tail end of October after regular number one Christopher Dillo was ruled out with injury.
But the 31-year-old Slovakian has impressed boss Danny Lennon in the 11 games since then and has now been declared Saints' first-choice keeper and rewarded with a new six-month deal.
Lennon told www.saintmirren.net: "Marian is exactly the type of player we want at our football club. He has great ability, is a tremendous character and he has brought a great presence and confidence to the group.
"Without doubt he is an outstanding professional with a great work ethic and he has a real desire to see the club progress. Marian is also a great role model for our younger keepers Christopher Dillo and Kieran Hughes as they look up to him for the standard that is required.
"I think it is fair to say that Marain has been a big part of the turnaround that we have had and I'm certainly glad that we have secured his services until the end of the season."
Lennon has also announced that loan signings David Cornell, Stephane Bahoken and Jake Caprice will be returning to their parent clubs after failing to make an impact in Paisley.