Correction appended, Oct. 12

Ben Carson said he would not be “compatible” on a ticket with Donald Trump.

During a question-and-answer period at the National Press Club, Carson was asked if he would consider the vice presidential slot in the Republican frontrunner’s campaign. He responded by saying the two wouldn’t make a good ticket.

“I believe that Donald Trump has been very useful because he brought in a lot of people, a lot of curiosity and enthusiasm,” Carson said. “And whoever the eventual nominee is will benefit from that. But in terms of Vice President, I would obviously want somebody who is compatible with me.”

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“The things that have to be done are very very serious things,” he added. “This can’t be tinkering around the edges… and I don’t think we have a whole lot of time to do that. So it would have to be somebody who is very compatible, somebody who understands the urgency of what we’re doing.”

Trump has been defending Carson in the press for comments Carson made in the wake of the Oregon shooting suggesting that he would have been more aggressive towards the shooter.

Correction: The original version of this story incorrectly quoted Ben Carson. Regarding racism he’s faced in his life, said said he is “concerned about the downtrodden people in our society.” And on the subject of Donald Trump as a running mate, he said, “in terms of Vice President, I would obviously want somebody who is compatible with me. The things that have to be done are very very serious things.. This can’t be tinkering around the edges… and I don’t think we have a whole lot of time to do that. So it would have to be somebody who is very compatible, somebody who understands the urgency of what we’re doing.”

Read More: Why Ben Carson Is Running for President

Write to Tessa Berenson at tessa.berenson@time.com.