Katharine McPhee tries on stunning wedding dress during fitting with future stepdaughter

Katharine McPhee is ready for her happily ever after with fiancé David Foster — and she already looks the part.

The 34-year-old "American Idol" alum recently tried on a stunning wedding dress along with a vintage veil during a dress fitting with Foster's youngest daughter, Jordan, 32. She gave fans a sneak peek at the silky-looking gown, which she stressed was not "the dress," on Instagram Wednesday.

"Wedding dress fittings today with @jordiefos! It was such a happy day. (It’s not the dress, but just wanted to share) ❤️," McPhee posted on the social media platform.

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The photograph, showing McPhee's reaction to the backless gown in the mirror, has already received nearly 35,000 likes.

"You're going to be a beautiful bride," one Instagram user replied.

"You look very beautiful blushing 👰," another agreed.

"U look so pretty and gorgeous Katharine 😊❤️," a fan added.

At 69, Foster is twice McPhee's age, but the pair hasn't let their 35-year age gap – or judgmental comments – get between them. And Foster's children have even voiced their support for the happy couple, who announced their engagement in July. It will be the second and fifth marriages for the bride and groom, respectively.

“I know that some people have been hating that relationship,” the record producer's daughter Amy told US Weekly weeks after the engagement. “All I can tell you is it absolutely works when you see them together.”

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"The Waitress" star has also defended her relationship, telling fans in July they should be “worrying more about registering to vote and midterm elections than who’s marrying me.”

The two have known each other for more than a decade. McPhee, then 22, first met Foster on the set of "American Idol" in 2006 when he was a guest mentor for contestants on the show.

Since then, the pair has collaborated on several live performances, including his 2008 PBS tribute concert “Hit Man: David Foster & Friends.” Foster even performed at McPhee's first wedding to Nick Cokas in 2008. He played the piano as the singer performed Natalie Cole and Nat King Cole’s hit “Unforgettable.”