He will travel with the team on their three-game road trip to Carolina, Tampa Bay and Florida.
Lernout, 22, was sent down to Laval following the Habs' 4-1 loss to the Edmonton Oilers on Saturday night. He skated for 14:43 of ice time at Rogers Place, registering a minus-1 differential.
In 30 games with the Rocket this season, the 6-foot-4, 214-pound defenseman has five points (1G, 4A), 20 penalty minutes and a minus-7 rating.
The native of Winnipeg, MB was the Canadiens' third-round pick (73rd overall) in 2014.