Occasional mistake

A worker who was being paid by the week approached his employer and held up his last paycheck.

"This is two hundred dollars less than we agreed on," he said.

"I know," the employer said. "But last week I overpaid you two hundred dollars, and you never complained."

"Well, I don't mind an occasional mistake," the worker answered, "but when it gets to be a habit, I feel I have to call it to your attention."