What's with the different oaths?

Did you notice that Chief Justice Roberts was sworn in with the following oath:

I, XXX, do solemnly swear, that I will support and defend the Constitution of the United States, against all enemies, foreign and domestic, that I will bear true faith and allegiance to the same, that I take this obligation freely, without any mental reservation or purpose of evasion, and that I will well and faithfully discharge the duties of the office of which I am about to enter, so help me God.

But the code specifies:

Each justice or judge of the United States shall take the following oath or affirmation before performing the duties of his office: “I, XXX XXX, do solemnly swear (or affirm) that I will administer justice without respect to persons, and do equal right to the poor and to the rich, and that I will faithfully and impartially discharge and perform all the duties incumbent upon me as XXX under the Constitution and laws of the United States. So help me God.” (28 USC 453).

What gives?  I'm sure it's noting really, but I just wondered.