Coca-Cola is rolling out a huge change in how it markets its signature drinks. For the first time, it’s going to promote Coke brands together, with Coke, Diet Coke, Coke Zero and Coke Life all under one worldwide marketing campaign. The company spent $3.5 billion on ads in 2014, so a change in how it markets its biggest brands is no small deal.

This move comes as the company is under pressure from Wall Street to perform in an environment where more shoppers worry about the health consequences sugary beverages and artificial sweeteners. Coca-Cola’s last quarterly report showed an 8 percent drop in Diet Coke sales.

Rolling the products into one global marketing campaign ensures consumers who worry about calories see Diet Coke, and those worried about artificial sweeteners see newcomer Coke Life. But there could be challenges to the unified approach.

“They’ve been so successful at defining these products as independent brands that I suspect there are a lot of people that may feel that Diet Coke is very different from regular Coca-Cola,” explained Omar Rodriguez‐Vila, a marketing professor at Georgia Tech and former Coke executive.

Coke is about to find out what happens when it tries to get its very different children to all play together.