Updated

Change isn't ever easy.

Diet Pepsi loyalists are using words like “yuck” and “undrinkable” to describe the new taste of Diet Pepsi now made with artificial sweetener sucralose instead of the more controversial aspartame.

Irate fans are taking to Twitter and other social media platforms to show their displeasure since PepsiCo Inc. replaced aspartame in August to try and reverse plunging industry wide diet-soda sales.

According to company surveys, the number one reason consumers were dropping diet cola was aspartame—a zero-calorie sweetener blamed for everything from autism to diabetes.

But Pepsi says that initial consumer sentiment often skews negative when established brands change.

“We’re not at all concerned,” said Seth Kaufman, chief marketing officer of PepsiCo North America Beverages told the Wall Street Journal.

Overall soda sales are on the decline, and before Pepsi rolled out the reformulated diet drink, its low-cal cola sales were down 6.5 percent over the previous year.