Wall Street rarely talks about its mistakes, but Citi Research admitted in a note to clients that it messed up with its previous call on Walmart.
Citi Research raised its rating for Walmart shares to buy from neutral, citing the company's e-commerce progress.
"We sat on the sideline with this name in '17, which proved to be a big mistake. Despite the stock's run-up, we think there is even more to come, particularly considering HD and COST are trading at a premium to WMT," analyst Kate McShane wrote in a note to clients Monday. "Our belief that its aggressive omnichannel strategy will continue to drive significant sales growth and WMT's ecommerce operations are emerging as a true challenger to Amazon, both factors that could fuel further multiple expansion."
Walmart shares were up about 1 percent Tuesday morning after the report.
The retailer is one of the market's best-performing large-cap stocks this year, rallying 42 percent through Monday versus the S&P 500's 20 percent gain.
McShane predicts Walmart will be able to report better-than-expected sales and profit margin results in the second half of 2018 due to "supply chain efficiencies" and its recent acquisitions.
As a result, she increased her fiscal 2019 earnings per share estimate for the retailer to $4.73 from $4.57.
Walmart's "grocery offerings, everyday-low-price positioning and increasingly-seamless integration of store-based and digital selling will ensure consistent B&M [brick and mortar] traffic trends," she wrote.
The analyst raised her price target for Walmart shares to $117 from $106, representing 20 percent upside to Monday's close.
— CNBC's Michael Bloom contributed to this story.