BTIG's Greenfield: I was wrong on Facebook. I'm upgrading the stock due to Instagram Stories.

A Facebook employee wears a shirt with the logo of the new Instagram video option during a press event at Facebook headquarters on June 20, 2013 in Menlo Park, California.
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Wall Street rarely talks about its mistakes, but BTIG admitted in a note to clients Tuesday that it messed up with its call on Facebook.

The firm raised its rating on the social network to buy from neutral because it believes the company's sales results will come in above Wall Street's expectations this year.

"Not having a buy on Facebook has clearly been a mistake in 2017 and we are simply not going to allow that mistake to continue," analyst Rich Greenfield wrote in the report. "The secular trends toward mobile devices globally and the accelerating shift of ad dollars are simply too strong to ignore, particularly with the unexpected strength of Instagram Stories and visible signs that Facebook video strategy is evolving from its early missteps centered on live video."

Facebook shares are up 22 percent this year through Monday compared with the return of 6 percent. The company reported better-than-expected fourth quarter earnings on Feb. 1.

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