McDonald’s is fighting to hold onto customers as the Big Mac turns 50, but it isn’t changing the makings of its most famous burger.

The company is celebrating the 1968 national launch of the double-decker sandwich whose ingredients of “two all-beef patties, special sauce, lettuce, cheese, pickles, onions and a sesame seed bun” were seared into American memories by a TV jingle. But the milestone comes as the company reduces its number of U.S. stores. McDonald’s said Thursday that customers are visiting less often.