Leeds have yet to lose a home game with the Danish goalkeeper in the side. Since his arrival, initially on loan, from Brondby eight months ago, Ankergren has won seven and drawn two of his nine appearances at Elland Road.
Ankergren missed the home defeat against Sheffield Wednesday on March 3 when Graham Stack, now at Wolves, deputised in 2-3 defeat.
"I am just delighted to be here," he said. "I had a chance to join a club that I knew would be playing in Europe this season but I really wanted to come back to Leeds instead.
"It was Leeds who came in for me when I needed them last season and I wanted to repay them. I haven't lost at Elland Road so far and it would be good if that continued.
"We made our home a fortress last season even though we were relegated and we know the other team will have to put in a lot of effort to take something away from us."