Walmart had a blockbuster 2020 in large part thanks to its booming e-commerce business buoyed by its large network of stores from where it could ship orders more quickly and from where customers could retrieve them faster.

Yet despite that success—Walmart’s U.S. business saw e-commerce grow 79%, making it the No 2 online retailer in 2020—the big box store remains far behind its longtime rival, Amazon, and will continue to be so this year, according to a forecast released on Monday by eMarketer.

The research firm expects Amazon to ring in sales of $367.2 billion this year, nearly six times more than the $64.6 billion it forecasts Walmart U.S. will rake in. What’s more, eMarketer expects Amazon, which already generates almost 40% of all e-commerce stateside, to win more market share.

Walmart has hardly been idle in its battle with Amazon. It has launched an express delivery service for groceries, one area of e-commerce where it has a clear upper hand over Amazon, as well as Walmart+, a subscription service similar to Amazon Prime.

“We’ve got a unique opportunity because of our stores. We’ve got all of the things available to us related to eCommerce growth,” Walmart CEO Doug McMillon told Wall Street last month.