The freestyle Frisbee event at the 11th Purina Incredible Dog Challenge will have to do without defending champion Wallace the pit bull, from Rochester, Minn. When owner Andrew Yori, 31, offered Wallace some cheese at the end of a spatula, the dog swallowed the plastic tip whole, The St. Louis Post Dispatch reported Wednesday.

Yori said vets first tried to extract the tip through endoscopy, and when that failed, Wallace went under the knife and was withdrawn from the Frisbee-catching contest. He'll have to take it easy for two weeks.

"It's classic Wallace," Yori told the newspaper. "It was like, 'Ummm, cheese,' then whoops! Down the hatch."

Wallace was the only pit bull in a crowd of border collies and Australian cattle dogs when he won last year's event, the Post-Dispatch said.