Oklahoma's football team was dominated by Iowa State in the second half and suffered a 38-31 loss to the Cyclones on Saturday at Owen Field in Norman.
After a shocking upset victory, Iowa State planted their flag on OU's midfield logo.
This comes four weeks after Baker Mayfield planted an OU flag at midfield at Ohio Stadium as his teammates celebrated around him.
The loss ended OU's nation-long 14-game winning streak, 17-game Big 12 winning streak and 18-game winning streak over Iowa State.
The Sooners got the ball first and marched 81 yards in just five plays, with Baker Mayfield passing over the middle to Trey Sermon for a 23-yard touchdown to cap the drive, putting OU up 7-0 with 12:35 to play in the first quarter.
Mayfield was 24 for 33 for 306 yards passing and 2 touchdowns, while Sermon ended with 90 yards rushing on 18 carries.
Oklahoma's second possession ended in a score as well, with Mayfield throwing a screen to CeeDee Lamb, who evaded tacklers and weaved through the secondary, leaning out to reach the ball over the left front pylon to complete a 15-yard touchdown and a 14-0 Sooners lead with 5:49 to play in the first quarter.
Iowa State responded with a 25-yard field goal from Garrett Owens to cut the OU lead to 14-3 with 1:20 to play in the first quarter.
The Sooners added to the lead early in the second quarter, with Austin Seibert kicking a 25-yard field goal to make it 17-3 with 11:53 to play in the second quarter.
The Cyclones then marched to their first touchdown, helped by a personal foul penalty on Ogbonnia Okoronkwo for piling on, setting up a 2-yard touchdown run by David Montgomery to cut OU's lead to 17-10 with 6:12 to play in the first half.
Oklahoma answered with a 75-yard drive in 8 plays, with Mayfield running it in from 13 yards out to give the Sooners a 24-10 lead with 2:43 to play in the second quarter.
Iowa State got a field goal before halftime, helped by a 54-yard pass from Kyle Kempt to Hakeem Butler, setting up a 32-yard field goal from Owens to make it 24-13 Sooners at halftime.
The Cyclones got another field goal early in the third quarter, a 42-yarder from Owens to make it 24-16 with 9:45 to play.
Oklahoma was marching to try to extend the lead, but a missed handoff between Mayfield and Sermon resulted in a recovered fumble by Joel Lanning at the Cyclones 6-yard line.
Iowa State then drove 94 yards to a touchdown, with Kempt passing to Marchie Murdock on a screen pass and scoring from 28 yards out.
The Cyclones went for a two point conversion and got it, with Kempt throwing to Allen Lazard to tie the game at 24 with 2:07 to play in the third quarter.
Oklahoma tried to regain the lead on the ensuing possession, but Austin Seibert missed a 45-yard field goal attempt wide right.
It took the Cyclones just two plays to take the lead, with Kempt passing in the right flat to Trever Ryen, who raced down the sidelines 57 yards for the touchdown to put ISU on top 31-24 with 12:46 to play.
The Sooners went 75 yards in 10 plays to tie it, with Mayfield passing to Mark Andrews for a gain of 26, setting up a 1-yard touchdown run by Dimitri Flowers to make it 31-31 with 7:18 to play.
Once again, Iowa State responded, this time with a 75-yard drive, finished off by a 26-yard touchdown pass from Kempt to Lazard on 3rd and 8, giving the Cyclones a 38-31 lead with just 2:19 to play.
Kempt was 18 of 24 passing for 343 yards and three touchdowns.
Oklahoma got the ball with a chance to tie it, but on 4th and 4, Mayfield threw incomplete and the Cyclones had upset Oklahoma.
Oklahoma had won 17 straight Big 12 games and and 18 straight vs. Iowa State, dating to a 1990 loss to the Cyclones in Norman.
The Sooners drop to 4-1 overall, 1-1 in Big 12.
OU will play Texas in Dallas next Saturday at 2:30 pm.