Shares of streaming music service Spotify fell Monday as investors grew nervous about a report suggesting that Amazon.com was preparing to launch a free, ad-supported music service.

Spotify (SPOT) stock, up roughly 20% in 2019, was recently down 3.8% to $139.50 following the publication of a Friday story by Billboard that said the Amazon music launch could happen this week. Amazon shares were trading essentially flat Monday afternoon, at $1,841.

Amazon (AMZN) didn’t respond to Barron’s request for comment in time for publication; a Spotify spokeswoman declined to comment. Some details were unclear, among them whether the new Amazon service would be marketed beyond Amazon’s Echo speakers.