The next time you buy a can of whipped cream in New York, be prepared to show some ID.

A little-known state law banning sales of cartridges used in cans of whipped cream to those under 21 has only recently been noticed — and enforced — to the amusement of customers unaware of the not-so-new regulation.

The age limit was enacted nine months ago to curb teens’ possible abuse of nitrous oxide, commonly known as laughing gas. The nitrous oxide found in whipped cream canisters, when it is abused as a narcotic, is commonly referred to as “whippits” or “whip-its.”