An upcoming royal garden party to welcome King Charles III to the United States has an unconventional take on the storied event.

Guests attending the party, set to take place at the British ambassador's residence in Washington D.C. during Charles and Queen Camilla's visit in late April, are being discouraged from wearing hats.

According to an invitation obtained by the Washington Examiner's Rob Crilly, along with a customary dress code of lounge suits and day dresses, the invitation reads, "Hats Not Encouraged."

USA TODAY has reached out to the White House for comment.

The dress code for a royal garden party, a tradition dating back centuries, includes lounge or business suits for men and day dresses for women, usually paired with hats or fascinators – headpieces consisting of feathers, flowers or beads. Men are also sometimes seen wearing top hats with their dress.