Authorities in Zhuhai City, China, said that they found heroin on a Nigerian man’s person after his unusual sandals got their suspicions up.

The unidentified man was arrested last week at the Gongbei Customs, according to China’s official news agency Xinhua. Police said that the sandals attracted their attention, and a search of the man’s luggage revealed another pair just like the one that he was wearing.

A search of all four sandals led to the discovery of more than two kilograms of heroin hidden inside the heels, police said.

Customs officials told Xinhua that traffickers have become increasingly clever about transporting their contraband, forcing officials to become more alert.