NEW YORK (AP) — In its latest push to establish itself as a purveyor of premium burgers, Wendy’s is testing a pretzel bun.

The Dublin, Ohio-based chain has started selling a bacon cheeseburger in select locations made with a slightly heartier, pretzel-like bun. A spokesman for Wendy’s declined to confirm the tests or provide any details, such as the price or where exactly it’s being offered. But the burger was spotted at a Wendy’s in Miami and others have posted pictures on the social media site Twitter.