YouTube has pulled the plug on a Chrome extension that used the site’s videos for a free, Spotify-like music streaming service.

Streamus, which launched in 2013, enabled free on-demand streaming of songs through Google’s Chrome browser. The Chrome extension tapped into YouTube’s catalog to power its streaming, but didn’t actually display any of the videos. Instead, it just used the audio, making it possible to stream songs in the background while doing other things online.

That concept — and the fact that Streamus was free and didn’t come with any ads — proved popular: The Chrome extension reportedly had 300,000 users.

However, it looks like YouTube wasn’t that happy about Streamus using its music in this way: The Google-owned video service apparently tried to work with the developer of Streamus for a few months to get him to change his app, according to a the Next Web report, but eventually just turned off access to its catalog a few days ago.

A YouTube spokesperson sent Variety the following statement when asked about the end of Streamus:

“We encourage people to leverage the power of our open API to embed YouTube videos in creative and innovative ways that comply with our terms of service.”

Streamus didn’t do that because it separated the audio from the video, something that’s expressively prohibited in YouTube’s terms of service. The Streamus app has since been removed from the Chrome Web Store, but there is still an open source version available.

The shut-down of Streamus comes at a time when YouTube is looking to double down on music streaming itself. The video site is currently running an invite-only beta test of its own Spotify competitor, dubbed YouTube Music Key.

One of Music Key’s features: Background playback, which essentially keeps the music playing without the video. Music Key will cost $10 a month when it becomes more widely available at some point later this year.