If you watch the video with this in mind, you can see Obama's amusement, followed by his decision to go ahead and say it Roberts's way.
According to the Huffington Post, Obama and Roberts re-did the oath on Wednesday night, just to be sure.
Craig, the White House lawyer, said in a statement Wednesday evening: "We believe the oath of office was administered effectively and that the president was sworn in appropriately yesterday. Yet the oath appears in the Constitution itself. And out of the abundance of caution, because there was one word out of sequence, Chief Justice John Roberts will administer the oath a second time."
The Constitution is clear about the exact wording of the oath and as a result, some constitutional experts have said that a do-over probably wasn't necessary but also couldn't hurt. Two other previous presidents have repeated the oath because of similar issues, Calvin Coolidge and Chester A. Arthur.