Weddings may bring you happily ever after — in bed.

One in five wedding guests say they have hooked up with someone in the wedding party in the past, according to a survey out this week of more than 3,000 people ages 21 to 65 who use the dating site Plenty of Fish. And it’s not just users on a dating site who are getting frisky: According to last year’s Real Weddings Study from The Knot, 19 percent of newlyweds said at least one of their guests had hooked up during or after the wedding.

So why are so many people getting frisky at weddings? More than half (52 percent) say weddings are a good place to hook up because it’s easy to start a conversation, the Plenty of Fish survey revealed. Another 21 percent said it was easy because everyone is trying to look their best, 15 percent admitted it was because the booze is flowing freely and 8 percent said it was because hookups at weddings often mean no commitment.

Another possible reason: “When you’re gathering your closest friends and family to celebrate your union, chances are your guests will have more than a few things in common,” The Knot explains of why this is so common.

It’s not just random hookups that are going down: 16 percent of people say they’ve met someone at a wedding whom they ended up going out with at least several times later. And in The Knot study, 4 percent of couples said a relationship that started as a hookup at the wedding ended up in a full-on commitment.

This likely comes as good news to those who are shelling out big bucks to attend another person’s nuptials. Data out last year from American Express found that — between the travel, clothing, gifts and other expenses — the average wedding guest ends up spending $703 to attend, up 5 percent from $673 in 2015. For millennials, the costs are even steeper: $893 on average.