If you walk through any downtown business center nowadays, you’re more likely to see men in suits wearing backpacks than carrying briefcases. And it’s not just young interns, but also senior executives. As part of the general casualization of American dress, backpacks have replaced traditional bags. If briefcases are still used, they’re typically softer leather ones instead of the hard-sided designs favored a generation ago.

We here at Put This On love backpacks, and use them ourselves, but they look awful with tailored clothing. Aside from the jarring combination, there’s also the damage you can put into your suit. I recently chatted with Edwin Deboise, founder and cutter behind the bespoke tailoring firm Steed, about the issue. He said the shoulder construction is likely to hold up fine, but the rest of the jacket may not.

“We use handmade wadding for our shoulders, but on many ready-to-wear suits, you’ll find a sponge-like material,” he says. “It’s pretty robust and will probably hold its shape, even if you sling a backpack across it. It’s really more about what happens to the cloth. If you throw a heavy bag across your shoulders, there’s naturally going to be a lot of rubbing against the material as you walk. For finer fabrics, such as wool flannel, you’ll eventually get a bit of burring. I really don’t recommend it.”

If you’ve made the effort to wear a nice suit, just carry a briefcase. Some are so sleek and minimally designed, they look inconspicuous anyway, even in the most casual of offices. See companies such as Frank Clegg Leatherworks and Linjer, who make softer leather bags that look a bit more easygoing than their stiffer, bridle leather counterparts (although, those are nice too). We have a full roundup of quality briefcase options here.