Harper posted a tweet Thursday that had a key word noticeably absent from Davis's title.
"I called Premier Designate of Newfoundland Paul Davis to congratulate him," Harper tweeted.
People on social media were quick to point out Davis was elected premier of Newfoundland and Labrador last week, not just Newfoundland.
"Forgot LABRADOR," tweeted Will Fowler in response to Harper's original tweet.
"When I say Newfoundland, I'm including Cape Breton, of course," said Garrett Barry.
Harper deleted the tweet, and sent out a new tweet with the full name of the province included.
"Tweeted too soon! Labrador you’re not forgotten, congratulations again to Premier Designate of Newfoundland and Labrador Paul Davis," Harper tweeted.
Davis was elected leader of the provincial Progressive Conservatives Saturday, also becoming premier-designate of Newfoundland and Labrador.