A few days before the start of the 2009 Tour de France, it was announced that Dekker had tested positive for EPO in a retroactive test carried out on a urine sample taken in December 2007. Dekker initially protested his innocence but he later admitted to using EPO, claiming it was a one-time mistake. He eventually admitted to using EPO over at least parts of the 2007 and 2008 seasons, although he declined to give exact dates. Dekker was suspended for two years, from 1 July 2009 to 30 June 2011.