A party bus was operating illegally when a bachelorette party attendee tumbled out of it in Kansas City, Kan., and was killed.

The Kansas City Star reported that the Midnight Express party bus in which 26-year-old victim Jamie Frecks was riding lacked the proper registration. Kansas law required it to have a proper U.S. Department of Transportation number, but it didn’t.

The Star reported that if the van would have been registered, DOT regulations would have triggered vehicle inspections. They might have caught some of the problems with the bus, including a malfunctioning “door ajar” warning system.

Transportation safety consultant Jim Hall says it’s appalling that the vehicle was permitted to operate for two years.

A Midnight Express attorney says the company has been cooperating with the investigation.