This should make the Spice Girls reunion tour even more interesting.

Mel "Scary Spice" B revealed she and Geri "Ginger Spice" Halliwell once had sex.

“She is going to hate me for this because she is all posh in a country house but it wasn’t a ‘thing,’" Mel B, 43, told Piers Morgan on "Life Stories" Friday. "It just happened, we just giggled at it and that was it," she said. "We were best friends. It just happened.”

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Geri Halliwell and Mel B (Ginger Spice and Scary Spice) of the Spice Girls (Getty)

Halliwell, 46, seems to have left her wild days behind her: She married Red Bull Formula 1 boss Christian Horner in 2015 and has two kids.

Mel lamented that since she revealed the bombshell, "[Halliwell] and her husband are going to kill me."

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The openly bisexual singer and former "America's Got Talent" judge refused to answer further questions about her sexual escapade with Ginger Spice, including whether or not it was "good," but said it was a "fun thing" and that Halliwell likely wouldn't deny it.

Mel B and Geri Halliwell (Scary and Ginger) of the Spice Girls photographed backstage at the Brit Awards in February 1997. (Getty)

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She also admitted to kissing Mel C (Sporty Spice), but said it was "nothing sexual" and was simply to show off and test out a new tongue piercing.

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Previously when asked about ever sleeping with her Spice Girl bandmates, Mel reportedly replied, “Do you mean sex, or did we just sleep in a bed together? Sex? Let’s just say I slept in a bed with them all.”