It was acknowledging Apple’s blink-and-miss dig at one of its closest rivals. Earlier this year, artist Taylor Swift pulled her music catalogue off Spotify, because she felt the service’s free, ad-supported business model doesn’t give the artist’s work its deserved value, BusinessInsider reports.

while Eddy Cue demoed Apple Music on stage, one of the screens showed Taylor Swift’s music listed on top. Seemingly acknowledging the dig, Ek tweeted, “Oh ok.” At the time of filing the story, Ek has deleted his tweet — not before we took a screenshot though.

When comparing the two services, Apple Music boasts a catalog of over 30 million songs, and will launch by the end of this month in over 100 countries. As for pricing, it will cost $9.99 per month or $14.99 for a family plan. As an introductory offer, the first three months will be free. The service also boasts a 24/7 radio called Beats1, and a social feature called Connect that lets artists and fans communicate with each other.

In comparison, while Spotify too has a catalogue of over 30 million songs, it is only available in 58 countries. Its userbase consists of over 60 million active users, with over 15 million of them paid subscribers. Users can subscribe to the service for $9.99 per month, wherein the first three months will only cost $0.99. It too has a family plan, wherein the first account will cost $9.99 per month, but additional accounts will only cost $4.99. There’s a student plan as well, which too costs $4.99 per month.