Spotify said on Tuesday that users of its premium services in the UK and Australia would now have 15 hours of free access to audiobooks a month, with the feature expanding to the United States later this year.

The music streaming giant is looking to supplement its earnings with other revenue-generating formats such as podcasts and audiobooks. The launch of its audiobook service in the United States last year challenged Amazon’s Audible.

Spotify last year laid out plans to get one billion users by 2030 and reach $100 billion in annual revenue. The company had also previously promised high-margin returns from its costly expansion into podcasts and audiobooks.

In July, Spotify raised prices for its premium plans across several countries including the United States and the UK.

The company said on Tuesday that subscribers will be able to choose from a catalog of over 150,000 audiobooks available as part of the existing Spotify Premium subscriptions, with the option to buy additional 10-hour allocations as top-ups.

Users must have a premium individual account or be the plan manager for their Family or Duo account in order to take advantage of this feature as of now, the company added.