Kansas blew a 10-point fourth-quarter lead, giving up 17 unanswered points as Northern Illinois rallied for a 30-23 victory on Saturday at Huskie Stadium in DeKalb, Ill.
KU's Tyler Patmon intercepted a Jordan Lynch pass an returned it for a touchdown with 14:33 left, but almost nothing went right for KU after that.
The Jayhawks had a holding penalty on the extra point, then Ron Doherty missed the 30-yard attempt wide right.
On NIU's next play from scrimmage, Lynch jump-passed to Martel Moore for a 65-yard TD pass.
Following a Mathew Sims 44-yard field goal that tied it with 7:58 left, Leighton Settle finished a 53-yard drive with a two-yard TD run to give NIU the lead.
KU went backwards five yards combined on its final two drives.
In his first game back from a three-game suspension, KU's James Sims rushed 18 times for 91 yards and two TDs.
Lynch was 23-for-35 for 235 yards passing with TDs and one interception. He added 22 rushes for 134 yards.
Dayne Crist finished 10-for-26 passing for 147 yards with no touchdowns and no interceptions.
KU (1-3) will have a bye week before playing at Kansas State on Oct. 6.