Lisbon has a fake drug problem, and government officials are worried it’s going to drive tourists away.

An army of ersatz dealers is hawking flour and ground-up bay leaves to unsuspecting foreign visitors — leaving local merchants and tour guides worried that Portugal’s recent tourism boom could fizzle.

Last year, a record 26 million tourists visited the European country, with a third of them taking in the Portuguese capital, according to statistics from the World Travel and Tourism Council. Tourism accounted for more than 19 percent of the country’s GDP in 2018, the organization said.

A police commissioner for the city’s criminal investigation department told Reuters the problem requires “continuous attention.”

“Tourists are unaware of this phenomenon so they are fooled,” said Bruno Pereira, adding the fake drug vendors make huge profits by showing potential buyers a sample of hashish or cocaine but then selling them ground up bay leaves or crushed Aspirin instead.

Police recently launched a campaign, with posters in popular tourist spots: “Need some seasoning? There’s cheaper bay leaf in the grocery store. Don’t buy fake drugs!”

The drug pushers have become so aggressive that tourists often take refuge in local bars to escape the constant hustle, a tour guide told Reuters.

“Everyone on my tours gets asked if they want drugs,” said Maarten, a local tour guide. “Some just laugh, but others don’t like it at all.”

Portugal decriminalized possession and consumption of drugs in 2001 to combat a high rate of heroin addiction and HIV in the country.