Polish swimmer Konrad Czerniak missed one of his scheduled races because the team did not register him.

Polish swimmer Konrad Czerniak was held out of Wednesday’s 100m freestyle qualification after Poland’s swimming federation failed to properly register him for the race, according to Polish media.

The Rio 2016 website lists the 100m freestyle as one of his events. Czerniak was supposed to race in qualifying on Tuesday but was scratched due to the oversight.

Czerniak wrote on Facebook that the news he would not be allowed to compete “knocked me off my feet.”

Czerniak was allowed to compete in the 4x100m freestyle relay on Sunday, though Poland did not qualify for the final. He will also compete in the 100m butterfly on Thursday.

Czerniak, 27, has won three medals in the butterfly at the world championships. He also competed at the 2012 Olympics, but did not medal.