Tiffany Haddish, Mark Ruffalo, Chris Rock, Amy Schumer and more stars are stripping down to bring attention to naked ballots while encouraging voters to properly follow vote-by-mail instructions.

In a new PSA created by RepresentUs, a non-partisan anti-corruption and pro-democracy group, celebrities including Naomi Campbell, Chelsea Handler and Sarah Silverman spotlight laws that require voters in 16 states, including swing state Pennsylvania, to insert their mail-in ballot into two separate envelopes in order to be counted. Ballots not inserted properly in states like Pennsylvania and New Jersey are considered “naked,” and rejected.

As the PSA explains, the “naked ballot rule” could result in the rejection of hundreds of thousands of mail-in votes, which would be a significant impact on election results in November.

“Naked ballots are the new hanging chads,” said RepresentUs co-founder and CEO Josh Silver. “The fact is that if you use the wrong pen color or don’t assemble your mail-in ballot correctly, your vote may not count. This is not a partisan issue; it affects all people planning to vote by mail. We’re grateful to this committed and talented group for making an eye-catching video so that everyone understands what they need to do to ensure their vote is counted.”

More information about naked ballots can be found here and watch the PSA below.