The surprise attendance of pop superstar Taylor Swift at Sunday’s Kansas City Chiefs game also brought an unexpected surge in sales of Chiefs’ tight end Travis Kelce’s jersey, according to sports retailer Fanatics.

The Fanatics network of sites, which includes NFLShop.com, saw a nearly 400% spike in sales yesterday, according to a spokesperson for Fanatics, the NFL’s official e-commerce partner.

Wearing a red and white team jacket, the singer cheered on the Chiefs during the FOX Sports broadcast. During the game at Arrowhead Stadium, she appeared to be chatting and laughing with Donna Kelce, the player’s mother.

Kelce’s relationship with Swift has been speculated for weeks by NFL broadcasters and the majority of Swifties, though neither has publicly confirmed it.