Miranda Lambert celebrated her boyfriend Anderson East's 28th birthday on Sunday by sharing a photo on Instagram of herself kissing the singer.

"Happy birthday to my favorite 'Bama' boy! @andersoneast [Photo by] @bfluke #candidkisses #withtheband #tourlove #rolltide #&erson #TexasBama," she captioned the picture.

The post was a rare display of public affection from Lambert, who prefers to keep her personal life private.

The former "Nashville Star" finalist once told Entertainment Weekly she believes in keeping "some mystery" online.

"I don't need to know what everybody's doing all the time -- especially with heroes of mine. I want to keep admiring them from afar," the star explained.

"[I'm] horrible at all of [social media]," she admitted. "To think of something clever or make sure you spell something right... I always have 14 people read [my posts] because I'm worried about all of it."

Lambert and East confirmed their relationship in December following Lambert's divorce from country singer and "The Voice" coach Blake Shelton in July 2015.

The pair made their red carpet debut as a couple at the Academy of Country Music Awards in April.

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"Whenever they are together they act like two free spirits," a source told E! News the same month. "Miranda adores Anderson. They understand each other."

"Anderson and Miranda are serious," another insider added. 'They have met both sides of their families. Both their families love what they have. They seem like they are in such a great place. They spend so much time together."

Lambert released a first single, "Vice," from her sixth studio album on Monday.

She last released Platinum in 2014, which debuted at No. 1 on the Billboard 200 and includes the singles "Automatic" and "Little Red Wagon."