Nsiala has made 13 appearances since joining the Reds in January.
"We're delighted to be keeping Toto," said boss Paul Cook in a club statement. "He's improving all the time and has come on hugely from when I first came into the club.
"He's a really commanding centre-half and we're really pleased with how he's shaping up. Long may it continue.
"Everton have been good enough to let him come here to learn as a young player and we're thankful they've allowed him to stay for longer."
Any reproduction, publication or redistribution of this material without the written agreement of 365 Media Group is strictly forbidden.