German Chancellor Angela Merkel’s favorite emoji is the smiley face, she revealed during a YouTube chat about global affairs Wednesday.

“When things go right, I even add a little heart,” the chancellor added, according to Politico EU.

But a new study says if you’re trying to make a good first impression at work, you shouldn’t use smiley-face emoticons in emails, as they may not convey the friendliness you’re hoping for. What’s more, they can negatively impact how coworkers perceive you.

“In general, we find that smiling (emoticons) are not actual smiles, and could be dangerous when used at work with unfamiliar colleagues,” study co-author Ella Glikson, a post-doctorate fellow at Ben-Gurion University of the Negev, told Moneyish in an email. “When people meet for the first time face to face, a smile is a great way to make a positive first impression, since it makes a person be seen as positive, friendly and competent. However, when meeting online in a work context, using smileys communicates incompetence, and has no effect on friendliness.”

“This negative perception of a person who uses smileys has also a negative effect on the willingness to share valuable information,” she added. “Thus, it may have negative long-term consequences.”

Glikson’s study, co-authored with researchers from Amsterdam University and the University of Haifa and published Monday in the journal Social Psychological and Personality Science, examined 549 people from 29 countries who were tasked with reading formal and informal work-related emails from unknown senders.

Across three experiments, the authors found that a photo of a smiling sender produced higher perceived warmth and competence — while a smiley emoticon gave off less competent vibes. Formal work emails without smiley emoticons were more likely to elicit more detailed responses, hence the authors’ finding that the happy glyphs “undermined information sharing.” And perceived competence and friendliness aside, recipients were more likely to assume the sender of a smiley email was a woman.

The new research has “practical implications for virtual first impression management,” the authors concluded.

“Although smileys may help convey a positive tone in written messages … their adverse effects on first impressions of competence may outweigh these benefits,” the trio wrote. “As such, our findings underline the common advice in business guides that the use of smileys in formal contexts should be avoided, regardless of age or gender.”

That’s not to say you shouldn’t use smileys or other emoji at all, Glikson clarified to Moneyish. “In fact, we find that when the topic of a conversation is informal, the negative bias towards using smileys disappears, and the writer is perceived as more friendly,” she said. “Furthermore, focusing on the first impression at work we did not test the effect of smileys in conversations among friends.”

The findings add to a growing body of research on how people should communicate at work. A 2013 study from the Florida Institute of Technology, for example, found that emoticon-laden emails reduced negative perception but came off less professional.

The emoticon decision can depend “on your level of seniority,” said career coach Melissa Llarena. “If it comes from a senior executive talking to someone who’s more junior … I think it demonstrates approachability,” she told Moneyish. “But if it’s coming from someone who’s more new to an organization, it can be misconstrued.”

Try asking your supervisor about how they’d like for you to communicate on the job, Llarena said. “You can totally ask questions like ‘Do you prefer that I communicate with you in person?’ ‘Is texting OK?’ ‘Are you more informal in terms of communication or would you like me to make sure that everything I give you can be forwarded to someone?’”

“In which case, you don’t want emoticons making their way around the organization — even if it’s something outstanding like ‘We just made $10 million (emoticon),’” she added. “You want to be able to deliver some work product that can be forwarded along.”

Etiquette expert Jacqueline Whitmore advised against using emoticons with a client “unless you have an established relationship.” “Oftentimes I’ll follow the client’s communication style, and if they use a smiley face, that tells me that it’s OK to use a smiley face,” she told Moneyish.

It also depends on your relationship with the recipient and your frequency of use. “If you overuse (emoticons), then it could come across in a more adverse way,” Whitmore said. “But if you use them sparingly, I don’t see anything wrong with it.”

This story was originally published Aug. 14, 2017 and updated Aug. 17, 2017, following a report of Merkel’s emoji preference.