As the NAACP readies for its national convention next month, some prominent officials with the nation’s oldest civil rights organization are questioning its recent endorsement of gay marriage, says NPR.

The Rev. Keith Ratliff, the NAACP leader in Iowa and Nebraska and an outspoken opponent of same-sex unions, has resigned from the group’s national board. The head of the organization’s Schenectady, N.Y., chapter also stepped down to protest the NAACP board’s approval last month of a resolution in favor of marriage equality.

“Clearly, this is an evolving conversation,” said Roslyn Brock, the NAACP’s national chairwoman. “And I believe that there are many in our organization who will still need to, or we hope will, evolve to a place where they can firmly stand with us. Some may never be able to come to terms with the resolution, and that’s fine.”

As civil-rights groups increasingly back same-sex marriage, gay rights organizers are becoming more active on issues of importance to the black and Latino communities, such as stop-and-frisk police policies and anti-immigration laws, according to The New York Times.