Today Nelson Peltz revealed that his firm Trian Fund Management LP holds 9.33 million shares of The Bank of New York Mellon Corporation (NYSE:BK). That amounts to about a .8% stake in the bank. Trian said in a regulatory filing with the Securities and Exchange Commission today that it had been keeping the stake confidential. The SEC had granted permission for the firm to do that, but this morning, that permission expired.

Nelson Peltz

Bank of New York Mellon climbs

Immediately after Nelson Peltz’s regulatory filing, shares of the Bank of New York Mellon climbed by nearly 5%. That was the largest intraday increase since July 17, 2013, reports Bloomberg Businessweek. Before this morning’s filing, the bank’s shares were only up by about 4% for the full year. However, that compares with the .4% decline for the S&P’s index of custody banks and asset managers.

A spokesperson for Bank of New York Mellon told Bloomberg Businessweek that they look forward to speaking with Trian, as the firm is well-respected.

Peltz keeps building stake in Bank of New York Mellon

The New York Times reports that Trian has continued to build up its stake in the Bank of New York Mellon. A spokesperson told the newspaper that as of last week, they had a $1.05 billion stake in the bank, or 28.9 million shares. She also said that someone from the firm had recently contacted the bank to talk about ways to “drive long-term growth and enhance shareholder value.”

Nelson Peltz and his firm are very well-known for taking stakes in companies and then working with their management to improve the companies’ performance. Other recent targets include Wendy’s (NASDAQ:WEN), Mondelez International (NASDAQ:MDLZ) and Ingersoll Rand (NYSE:IR).

This isn’t the first time Peltz has worked with banks. In 2011, his firm took a stake in State Street with the goal of getting management to spin off the bank’s money management unit. State Street Corporation (NYSE:STT) did not end up doing that, although it did return capital to shareholders and also reduce costs. Trian sold out of State Street in November.