Denver voters will decide in May whether to decriminalize so-called magic mushrooms containing the hallucinogenic drug psilocybin.

KMGH-TV reported Friday that city elections officials determined that proponents gathered enough valid petition signatures to put the proposal on the May 7 municipal election ballot.

If it passes, it’s believed Denver would be the first U.S. city to decriminalize the drug.

However, it would still be illegal under federal law. The U.S. Drug Enforcement Agency classifies psilocybin in the same category as heroin and LSD.

The DEA also puts marijuana in that category. Colorado, nine other states and Washington, D.C., allow recreational marijuana use by adults, and the federal government has not moved to shut them down.

Denver voters decriminalized marijuana before voters statewide took the same step in 2012.