Heidi Klum (Erika Goldring/GETTY IMAGES)

Judge-flation has hit “America’s Got Talent.”

One season after the addition of Howard Stern, at a reported cost of $20 million, failed to goose the ratings on NBC’s summer reality series — the ratings, in fact, fell noticeably — NBC announced Monday its next big idea: adding a fourth judge.

That judge: Heidi Klum, the statuesque, wooden host of “Project Runway.”

“As we look to develop an act that will get the world’s attention, we and the contestants will benefit from Heidi’s international sensibility and understanding of what works in today’s global entertainment industry,” enthused Paul Telegdy, NBC’s head of alternative programming.

“Heidi Klum brings huge experience to ‘America’s Got Talent’ from her background as a model, designer, actress, TV host, producer, and successful businesswoman,” chimed in “AGT” executive producer Trish Kinane.

“America’s Got some serious Talent!” explained Klum.

It’ll mark the first time in the show’s history it will have had a four-judge panel. Klum will be joining Stern, Howie Mandel and Mel B (aka Melanie Brown), who is also new to the show, replacing Sharon Osbourne who left at the end of last season.

“AGT” isn’t the first competition show to feature four judges: NBC’s own “The Voice” has four; Simon Cowell’s stumbling singing show “The X Factor” has four judges” and Fox’s “American Idol” has tried both four and three.

But it’s the first time a competition show has hired a fourth judge one season after shelling out $20 mil to hire “the king of all media” — not to mention the cost of moving the show to New York for KoaM’s convenience — because that was going to be a ratings game changer for the show.

Last May, about 10.48 million people tuned in to watch Stern’s debut on “AGT.” That’s about 32 percent fewer viewers than the 15.3 million who’d watched the previous season debut.

Among 18-to-49-year-old viewers who are the currency of NBC’s ad sales, Stern’s unveiling came in 14 percent short of the previous season starter.

Meanwhile, former Victoria’s Secret undies model Klum, cut her teeth on reality competition as the host/judge on “Project Runway” which famously moved from Bravo to Lifetime network, causing much uproar in the biz. “Project Runway,” in its most recent iteration, averaged 2.5 million viewers.