A widely followed financial analyst upgraded shares of Morgan Stanley on Wednesday and said he's now bullish on every big U.S. bank.

"We reiterate our bull case on the largest US wholesale banks and now recommend 5 of 5 with an upgrade of Morgan Stanley from market perform to outperform," Wells Fargo's Mike Mayo said in am investor note titled "All-in on U.S. Global Banks."

"Long-term, MS has evolved its business mix more than any other large bank with an increase in wealth and asset management to 1/2 the firm from 1/3 earlier this decade," Mayo said.

The long-time analyst known for his tough questioning of executives — and for a time, bearish view of the sector — raised his price target for Morgan Stanley to $60 from $56. Morgan Stanley shares closed Tuesday at $44.52 and were little changed in premarket trading on Wednesday.

Bank stocks have struggled lately even with interest rates rising and the firms reporting strong results. Morgan Stanley's third-quarter earnings topped the Street last week as investment banking revenue climbed.

"Results this year and in 3Q18 reflected better than expected trends in trading, wealth and investment management, and revenues," Mayo wrote.

Yet Morgan Stanley shares are down 8 percent in the last month and 15 percent in 2018.