“A joke’s a very serious thing,” wrote Charles Churchill in 1762. The truth of that statement hasn’t diminished in almost 250 years. Jokes are serious in the workplace because new research shows that making co-workers laugh with work-related humor builds team spirit and stimulates creativity. But the wrong kind of humor can split your team apart and ruin careers.

The hardest part of your problem is calling people on their racism without alienating them. The best technique is to have a short, private talk with each person, and to focus your conversation on helpful suggestions rather than criticism. You might start with, “I’m sure you meant no harm, but the jokes you just told can be perceived as negative.” Then point out that these negative perceptions usually reflect poorly on the person telling the joke, and that you don’t want him or her to be perceived as rude or racist.

This approach communicates that the jokes are inappropriate, and the behavior unacceptable. You’ve also inflicted as little damage as possible to your working relationship by giving your co-workers the benefit of the doubt — assuming they’re not racist but instead simply have poor taste in humor. If your conversation doesn’t stop the racist jokes, it’s time to have a confidential conversation with management or your human-resources department to put an end to the offensive humor.