Supporters of Sen. Bernie Sanders’ (I-VT) have filed a lawsuit seeking an extension for voter registration in the June 7 presidential primary in California, the Los Angeles Times reported Sunday.

William Simpich, the attorney that filed the lawsuit, told the LA Times that California voters are confused about the primary process in the state. He said that many voters who are not affiliated with a political party are not aware that they can still vote in the open Democratic primary.

In the lawsuit, Simpich calls for California officials to launch a public awareness campaign to educate California voters on the rules for the presidential primary by March 31, the deadline for requesting a mail-in ballot. The lawsuit also asks that the deadline for registering to vote be extended until June 7, the day of the primary.

The lawsuit was filed on behalf of two voters in the Bay Area, as well as the American Independent Party. The Voting Rights Defense Project, a group supporting Sanders, is also listed as a plaintiff, according to the LA Times.