The UFC has docked one of its champions for not wearing the proper Reebok apparel during a fight week activity.

Rafael dos Anjos, the UFC lightweight champion, was fined a "significant" amount for violating the promotion's Athlete Outfitting Policy at UFC on FOX 17 weigh-ins Dec. 18, sources told MMA Fighting.

Dos Anjos (25-7) was wearing an Evolve MMA shirt briefly before hitting the scale. The Brazilian trains part of the time at Evolve in Singapore, along with Kings MMA in Huntington Beach, Calif. The Evolve website lists dos Anjos as an instructor and says he has been part of the team since 2009. Dos Anjos has a close relationship with Evolve owner Chatri Sityodtong.

Donald Cerrone and Nate Diaz, both of whom also fought at UFC on FOX 17 in Orlando, have been public about being fined by the UFC for violating the Outfitting Policy. Cerrone said Monday on The MMA Hour that he was penalized "quite a bit more" than $5,000 for wearing a piece of an American flag sewn onto his fight shorts. Diaz implied in a tweet Sunday night that he was fined for wearing jeans at weigh-ins.

The UFC has not spoken out on either situation. When reached by MMA Fighting, dos Anjos' manager Ali Abdel-Aziz declined to comment.

UFC senior vice president of global consumer products Tracey Bleczinski told MMAjunkie last week that three fighters from UFC on FOX 17 were fined for "serious" infractions of the Athlete Outfitting Policy. She didn't mention any names. Twelve others were warned since the uniform deal with Reebok went into place in July, Bleczinski said. Fighters and coaches are not allowed to wear apparel other than Reebok during fight week and in the Octagon, the policy stipulates.

Dos Anjos beat Cerrone via first-round TKO in the main event of UFC on FOX 17 to retain his lightweight title. He has held the belt since beating Anthony Pettis at UFC 185 in March 2015.

UFC champions make $40,000 from the Reebok deal per fight. Challengers, like Cerrone, make $30,000.