Diet Pepsi Cola may be going back to using aspartame, a report in Ad Age claims. The diet soft drink brand may experience a sweetener reversal since PepsiCo pulled the artificial sweetener in 2015, in a marketing move over safety concerns, and replaced it with sucralose and Ace-K.

The company faced a consumer backlash when it dropped aspartame from Diet Pepsi. So in 2016, it resurrected the aspartame version—only in limited quantities, and marketed it as “classic sweetener blend.” It kept the aspartame-free version as its mainstream variety. Now, Diet Pepsi is said to be going back to the version with the controversial sweetener as the soda’s main variety, reports Ad Age. 

A PepsiCo spokesperson confirmed the switch, but didn’t comment further, Ad Agereports. The move sets up a new chapter in the cola wars with Diet Pepsi’s overhaul going head-to-head with Diet Coke, which has also undergone big changes. Diet Coke recently launched new flavors and packaging, and has stayed with aspartame despite criticism of the sweetener by some health activists. The move has paid off, as sales were said to increase by 10 percent over 2017.

PepsiCo’s strategy this year reportedly calls for boosting marketing behind its established soda brands and promoting its new Bubly sparkling water brand.

On a recent earnings call, PepsiCo’s CEO Indra Nooyi told investors, “Let’s not forget, 2015 and 2016 were very good years for North American Beverages. 2017 was a year that we would have liked to have had better performance. And now we’re going into 2018 with a strong marketing calendar. So, let’s wait for the year to play out.”