They’ve got a latte nerve!

The owner of Manhattan Espresso, a tiny Midtown coffee shop, says he got a “B” grade from inspectors because his front door was open on a busy summer day.

“In July, I want the door closed, because I don’t want to air-condition 49th Street,” a frustrated Brad Bonewell told The Post. “But they [customers] can’t form a line when the door is closed.”

When fruit flies snuck in the open door and hovered over bananas on the counter, Bonewell was cited for conditions “conducive to pest life.”

He also was cited for the fruit flies and for his server’s failure to use “effective hair restraint” — all adding up to the “B” grade.

In August, Bonewell told a hearing officer his shop door has a self-closing hinge, but was being held open by customers. When the officer sustained the “B,” Bonewell appealed and lost again last week.

“That’s ludicrous,” said customer Lea Gross, 29, of Murray Hill. “Every store on the block has their door open . . . they were looking for problems that aren’t there.”