Martin Truex Jr. was on his way to a top-12 start in the Daytona 500, but then it all fell apart.

Well, not everything – just his car window.

One of the windows on Truex’s car fell off during the final lap of the first Budweiser Duel on Thursday in Daytona Beach, Fla., and he was black-flagged by race officials, dropping him from sixth to 19th. The two Duels determine the starting order for the Daytona 500 on Sunday.

Truex, a Stafford Township native, explained what happened in a series of Twitter posts shortly after the race:

“Well we had a decent race,” he wrote. “@napaknowhow car handled great again, just need a little more speed. Oh and keep the side window attached. … These cars create a lot of turbulence in the draft, it broke the window track where the side window clips are attached. … We went from 5th or 6th to last car on lead lap. … I really wish the (darn) thing fell out earlier so we coulda fixed it. Not much u can do when it falls out the last lap.”

Truex then was asked by ESPN reporter Marty Smith via Twitter if the air pressure “just sucked it out of the frame.”

“It broke the metal where the clips attach, then..” Truex replied.