 Petry stayed as a permanent member of the Oilers for the lockout-shortened 2012–13 season, playing in all 48 games as the Oilers again failed to make the Stanley Cup playoffs that year.On March 2, 2015, during the 2014–15 season, Petry was traded to the Montreal Canadiens in exchange for a 2015 second-round draft pick and conditional fifth-round pick.After the Canadiens post-season run, on June 2, 2015, Petry opted to surrender his impending free agent status in signing a six-year contract extension with the Montreal Canadiens until the 2020–21 season.