Spotify introduced real-time lyrics in 2021 for free and Premium users worldwide, but some listeners on the free tier noticed this week that the music-streaming service had locked these lyrics behind a paywall.

As The Verge reports, some people are seeing a notification that says: “Enjoy lyrics on Spotify Premium" overlayed on top of the menu that normally displays lyrics as a song plays.

Spotify tells The Verge that the feature is a routine test being shown to "a limited number of users in a pair of markets.”

The test comes shortly after Spotify increased the price of its Premium service from $9.99 to $10.99 per month, putting it more in line with some of its streaming rivals. Spotify justified the move as a way to "keep innovating [and] deliver value to fans and artists on our platform."

Licensing deals aren't cheap, and over the years, Spotify has experimented with a variety of ways to make money, from music videos and audiobooks to podcasts. Despite a billion-dollar investment, however, it's had limited success on podcasts, The Wall Street Journal reports.

As The Verge notes, Spotify's most notable Premium-only feature is probably its AI-based DJ, which adds an AI voice who acts as a host and guides you through a personalized radio station.

Music lyrics are readily available on the internet, and have been available to Spotify free users for years, so it remains to be seen if access to them will be worth $10.99 per month.