Chief Justice John Roberts has administered the presidential oath of office to Barack Obama for a second time just to be on the safe side.

The unusual step came after Roberts flubbed the oath a bit on Tuesday, causing Obama to repeat the wording differently than as prescribed in the Constitution.

White House counsel Greg Craig said Obama took the oath from Roberts again out of an abundance of caution.

The chief justice and the president handled the matter privately in the Map Room on Wednesday night.