Spotify’s subscriber base has grown a lot in just the last six months.

On Wednesday, Spotify CEO Daniel Ek tweeted that “40 is the new 30,” seemingly in reference to the millions of people who now pay monthly to listen to his streaming service ad-free. Previously, Spotify reported 30 million subscribers in March, meaning that the service has racked up about 10 million new subscribers in half a year.

40 is the new 30.

Million. 😄 — Daniel Ek (@eldsjal) September 14, 2016

Last week, Spotify’s biggest competitor, Apple Music, announced that it had reached 17 million paying subscribers. In February, Apple Music boasted 11 million users, and that figure continued to go up steadily to 13 million in April, and then to 15 million in June.

It seemed that Apple Music had been growing at a faster pace than all its competitors, but now Spotify proves to be the clear winner, successfully converting more of its 100 million users into paid subscribers.

Spotify has a free, ad-supported tier where users can listen to the entire catalog but have limited capabilities when it comes to mobile and offline listening. Paid subscribers don’t hear any commercials and can listen to any song on-demand using the Spotify apps. Apple Music gives all users a three-month free trial, but then users have to become paid subscribers to continue to listen. Both services cost $10 a month.

Why this matters: Spotify was certainly feeling the heat after Apple Music garnered 17 million paid subscribers in a little over a year. More than any other tech giant, the iPhone maker has the money and the connections to be a formidable threat. Not to mention, Spotify has been playing on Apple’s turf from the get-go.

But Spotify has managed to not only stay afloat, but thrive—despite the fact that Spotify has lacked the splashy exclusives that seem to drive Apple Music’s strategy. In the last year, Adele, Beyoncé, Coldplay, Rihanna, Drake, Kanye West, and Frank Ocean have withheld or delayed new music from appearing on Spotify. It may be that Apple’s entry into the streaming music landscape has been the rising tide that lifts all boats, making iPhone users more comfortable with the idea of paying for music subscriptions.

Spotify reaching 40 million subscribers couldn’t come at a better time. Spotify’s biggest challenge has been converting free users into paid subscribers in order to sustain its business over the long haul—even if those paid subscribers have to wait to listen to a new song by Beyoncé.