D-Day historian Paul Woodadge told the BBC that the mistake was "quite shocking."
"It's going to be the 75th anniversary of D-Day -- the last one where there's any veterans around who will remember it,” Woodadge told the network. "These stamps are the kind of thing people will buy for their fathers and grandfathers."
A Royal Mail spokeswoman was quick to apologize.
“We work very hard to ensure that our Special Stamp programme appropriately commemorates anniversaries and events that are relevant to UK heritage and life,” she said in a statement. “We would like to offer our sincere apologies that our preview release for our 2019 Special Stamp program included a stamp design which had been incorrectly associated with the D-Day landings.
“We can confirm that this image will not be part of the final set, which will be issued in June 2019.”