McDonald’s (NYSE:MCD) is going to be testing all-day breakfast.

The first McDonald’s retaurants that will offer all-day breakfast will be located in San Diego. The restaurant chain may decide to expand its all-day breakfast offering to more locations if the tests are successful, reports Business Insider.

One potential problem for McDonald’s all-day breakfast is the company’s grills. The grill aren’t large enough to handle both breakfast and lunch. This is why many locations stop serving breakfast items at 10:30 a.m., Business Insider notes.

“We look forward to learning from this test, and it’s premature to speculate on any outcomes,” Terri Hickey, a McDonald’s spokesperson, told The Guardian. “We’re excited to serve our customers in this area some of McDonald’s great-tasting breakfast sandwiches, hash browns and other favorites all day long.”

MCD shares were up slightly as of Monday evening.

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