Coming to work cranky is probably a good idea – because grumpy workers are the most creative and productive, says a new study.

“Bad moods and negative attitudes have gotten a bad rap at work,” said Jing Zhou, a management professor at Rice University in Houston. “As it turns out, those perennially happy, smiling employees may not be the most creative or productive at the office.”

His study said that bad moods are naturally produced almost any time people work together, but the grumpiness can be harnessed to help the bottom line.

“If you want creativity that leads to innovation in your workplace, those naturally occurring bad moods can play a fruitful role – in fact, they’re necessary to make things better,” he said.

The professor said he’s not encouraging bosses to promote bad moods among his workers.

Instead, those cranky moments can be used to “identify potential problems and think of ways to improve things.”