Sun Yang’s national 1,500-meter freestyle title was stripped as the star swimmer had failed a doping test during the national championships this May, announced the Zhejiang Swimming Association Monday.

The multi-Olympic and world champion tested positive for stimulant trimetazidine on May 17 during the national swimming championships and had been banned for three months till August 16, China Anti-Doping Agency said on Monday.

“I have taken many doping tests during years of training and competition and I had never failed one before,” said Sun, the Zhejiang native, who was also fined 5,000 RMB (about 816 US dollars).

“I was shocked and depressed at that time, but at the same time it made me cherish my sporting life even more. I will take it as a lesson and be more careful in the future.”

Olympic and world champion swimmer Sun Yang’s short suspension for a doping violation in May was “appropriate”, a senior Chinese anti-doping official said on Monday, defending the delayed announcement and lenient punishment.

Sun’s short suspension and CHINADA’s late announcement sparked widespread debate.

“This case met the World Anti-Doping Agency’s punishment-reducing requirements, but Sun was still counted responsible for not declaring medicines he was taking beforehand, so imposing a three-month ban was appropriate.”

Trimetazidine, a drug for cardiac diseases, was listed by the World Anti-Doping Agency in January as a prohibited “specified stimulant”, which is considered more susceptible to inadvertent use and can carry reduced penalties.

Zhao said WADA only banned athletes from taking the substance during competitions, which means Sun’s long-term medication during training was legal.

Sun posted a statement about the doping violation on his personal micro blog account on Monday evening.

“For whatever reason, an athlete should be responsible for any substance taken, so I fully accepted the punishment and had made deep reflections on my mistake. Swimming is my life. I will train harder and control myself more strictly from now on to pay back my supporters with more glories,” he said in the statement.

In response to the timing of the announcement, Zhao said CHINADA’s heavy workload from May to October, during which it handled about 9,900 tests for the Nanjing Youth Olympics and Asian Games, delayed the analysis and statistical procedures.

But not everyone accepts this explanation.

“The swimming association issued the light punishment hurriedly in the swimming offseason before Sun’s violation was even reported. It couldn’t be more obvious that it was to protect him,” said a sohu.com report on Monday.

Neither Sun nor the swimming association was available for further comment on the punishment.

Earlier this year, in February during the Sochi Winter Olympics, Ukrainian cross-country skier Marina Lisogor also failed an in-competition doping test for trimetazidine and was expelled from the Games.

“Athletes and coaches should take the recent cases as a wake-up call for better anti-doping education and more sensitive medication precaution,” Zhao said.