It’s a flap over a cap.

An ad industry watchdog wants MillerCoors to modify its claims about flagship Miller Lite because it hasn’t made changes as the ads imply.

It’s a basic marketing tactic to tout a product attribute, especially if it’s new, to increase shoppers’ interest.

In this case, MillerCoors started advertising flagship Miller Lite’s “Taste Protector” caps and lids last summer. But MillerCoors acknowledges the tops don’t use new technology so its ads can’t imply they do, the National Advertising Division Council of Better Business Bureaus said Wednesday.

The industry body, known as NAD, looked into the matter after beer-making rival Anheuser-Busch Inc. complained. Many of its inquiries start with complaints by rivals.

MillerCoors has been saying the new golden tops and lids on Miller Lite, which has been in a sales slump, have a special seal that “locks out air and locks in that Great Pilsner Taste.”

NAD said in its nonbinding decision that MillerCoors should stop referring to a “special seal” and not imply the product has changed.

“While advertisers can change marketing strategies to promote the different features of their product, they must do so truthfully to avoid any potential overstatement or consumer confusion,” the board said.

In highlighting aspects of their products, companies can’t mislead, said Doug Stayman, associate dean of MBA programs at Cornell University’s Johnson School of Management.

“There’s a tremendous amount of pressure on them to come out with something new and different,” he said. “And there’s a fine line. But this seems to be over it.”

MillerCoors said it will take the ruling into consideration for future advertisements. It was pleased NAD agreed it could use “Taste Protector” statements but disagreed with objections to the word “special” — although it’s been removed from packaging.

More about In Cap Flap, Miller Lite Told to Change Beer Ads here.