Diego Corrales retained his world lightweight boxing titles despite being stopped by Jose Luis Castillo in the fourth round of their fight on Saturday after his opponent failed to make the weight limit.

The fight went ahead even though Mexican Castillo was over the 135-pound (61.24-kg) category limit at Friday's weigh-in, meaning that Corrales' World Boxing Council (WBC) and World Boxing Organization (WBO) titles were not put on the line.

Castillo, 31, was fined $120,000 by the Nevada State Athletic Commission for failing to make the weight and the fight was downgraded to a non-title bout.

American Corrales, who had knocked out Castillo in the 10th round of a title unification bout in May, was counted out by referee Joe Cortez after being battered by a left hook from the Mexican 47 seconds into the fourth of 12 scheduled rounds.