Sometimes, even electric vehicles aren’t good enough for the die-hard green car set.

An electric car advocacy group on Tuesday criticized California’s influential air quality regulator, the California Air Resources Board, for allowing BMW’s one-year pilot program of electric Mini Coopers to earn the same credit towards the state’s clean vehicle program as standard production cars.

California is requiring that automakers, collectively, put 7,500 zero-emissions vehicles, or ZEVs, on its roads.

But Plug In America on Tuesday said there is a “gaping loophole” in the program that “could deal a blow to the proliferation of plug-in vehicles.”

Specifically, the group targeted BMW’s leasing program of 500 electric Mini Coopers, which it calls MINI Es.