That makes it "repugnant" to the U.S. Constitution, Article VI, Clause 3 specifically.
It was an omission by accident, but it has never been corrected for the past 112 years. It's about time it be corrected.
By the way, the FIRST act of the U.S. Congress during its FIRST session (when George Washington was President) was that all Federal officers and officers of the several states, within three days of this FIRST bill's passage, "take the oath to support the Constitution."
That's how important the oath of office is.
It is also spelled out in Title 4, Section 101 of the U.S. Code, where state officers of the three branches of government must, before they assume the duties of their office, take an oath "to support the Constitution."