Grimes revealed she and Elon Musk changed their baby's name because it didn't comply with a California law.

Just when we had finally learned how to spell X Æ A-12, the Canadian singer-songwriter announced she made a small adjustment to her son’s unusual name because the California state constitution forbids the inclusion of any numbers. (Names can only use the 26 alphabetical characters of the English language.)

Grimes confirmed the update after an Instagram user asked, "Did you change the baby name because of Californian laws? What is the baby’s new name?"

"X Æ A-Xii,” she replied, adding, "Roman numerals. Looks better tbh."

So, instead of changing their newborn's name to something else on his birth certificate, Grimes and Musk just changed the number 12 to Roman numerals. Luckily, it’s pronounced the same.

Meanwhile, the Tesla CEO explained how to pronounce X Æ A-12 during an appearance on the Joe Rogan Experience, saying, "It’s just X, the letter X, and then the Æ is pronounced ‘Ash’ and then A-12 is my contribution. Archangel 12, the precursor to the SR-71. Coolest plane ever. It’s true.”

Grimes also tried to explain the name's meaning via Twitter earlier this month.

The couple welcomed their first child together on May 4.