The 39-year-old singer took to Twitter on Monday to celebrate the 21st anniversary of her 1999 debut, and some of her followers were quick to ask her what had happened to the 20th anniversary edition that was supposed to be released.

"Happy 21st anniversary to my debut, self titled album," she tweeted. "So crazy - 21 years ago, I scored Reflection and my record deal in the same week.

"Fast forward to today, the 21st anniversary is falling on the same week my new rendition of Reflection is dropping. The stars are aligning."

While fans were happy to celebrate the milestone, others questioned what had happened to plans for the 20th anniversary re-release that the star had teased last year.

"Haha 100 per cent fair point! I never forgot about it & was disappointed that it never came to fruition," Christina responded. "Originally I wanted reimagined new material to coincide with the digital release. But due to timing with touring & Vegas, it wasn't able to be done to my standard of quality."

She continued: "So I decided to postpone to when the time felt right. Anything worth doing is worth doing right...so I will definitely readdress this in the future. Thanks for bringing to my attention. I never want to 'settle' in giving you my best always."