JPMorgan Chase’s board said Friday that it was standing behind Jamie Dimon, the bank’s chairman and chief executive, in the face of calls from some investors that the two jobs be split.

In the bank’s proxy filing, the 11-member board said Dimon should continue to hold both positions, as he has since 2006. “The board has determined that the most effective leadership model for the firm currently is that Mr. Dimon serves as both,” the filing said.