Carnival Cruise Line is praising tippers who prepay with stickers. Not everyone's happy about it.

Carnival Cruise Line is putting "Crew Love" stickers on the Sail & Sign cards of passengers who prepaid for gratuities, Cruise Critic reported this week. And, unexpectedly, the public display of tipping affection is receiving a bit of backlash.

"The 'Crew Love' stickers … are simply a way to let our crew know that a guest has prepaid their gratuities, while giving those guests a little recognition for their generosity," a Carnival spokesperson said in an e-mailed statement to Yahoo Travel. The statement noted that the Crew Love stickers, along with in-cabin thank-you notes, are just one part of a larger pilot program. "We're listening to feedback as we evaluate it," the statement adds.

The round sticker, which cruisers have shared photos of online, reads "Crew Love, I pre-paid my gratuities." And it seems to be stirring up the most discontent, since it publicly identifies who has, and thus has not, prepaid their tips.

But travelers should keep in mind that many cruise lines (including Carnival) charge per-person, per-day gratuities. Carnival Cruise Line sets that amount at $17 per person, per day (and $19 for suite guests). Cruisers can either opt to prepay those gratuities or pay them at the end of the sailing with their final statement. Cruisers can also request that the charges be removed, but automatic gratuities on cruises are often thought of as a "service charge" that's distributed among crew members.

Cruisers can also tip crew members who go the extra nautical mile. The Carnival spokesperson also pointed to a Carnival page stating that a 20% service charge is added to drinks, and that head waiters can be tipped based on their "quality of service."

Frustration toward the "Crew Love" stickers seems mostly centered around the performance of it. One commenter on Reddit's r/Cruises subreddit described it as "public shaming." Others are thrilled. "I love it," wrote another on the r/CarnivalCruiseFans subreddit. "If it means I'll get better treatment from the staff because they know I prepaid then I don't see a problem with it."