Madonna may be letting her daughter Lourdes grow up a little too fast -- judging by Instagram photos of the 17-year-old holding a glass of wine at a pre-prom party.

The Material Mom shared the snapshot of Lourdes and a couple of pals all dressed up and seemingly drinking vino -- despite being four years shy of the legal drinking age.

Less than six months ago, Madonna raised eyebrows by tweeting a photo of her 13-year-old son Rocco and his pals posing with bottles of booze.

photo: getty images/Madonna on Instagram