In the last couple of years, if you type a song title into Google, you’ll get a box that includes its lyrics, alongside the usual search results. It’s a useful tool, but one company that specializes in song lyrics, Genius Media, says Google has been copying their lyrics for years for its search results without credit.

Genius has been around since 2009, and it describes itself as a platform “platform for annotating clever rap lyrics,” and has since expanded into other types of music, and a place for music fans to annotate and discuss their favorite songs. Genius Media says that Google has been copying its lyrics, according to The Wall Street Journal. The site says that it’s brought up its complaint with the search giant for years.

In a statement to The Verge, Genius Chief Strategy Officer Ben Gross said that the company has “shown Google irrefutable evidence again and again that they are displaying lyrics copied from Genius in their Lyrics OneBox. This is a serious issue, and Google needs to address it.”

The site employed a neat trick to figure out if its lyrics are actually being copied and reposted: it uses a series of alternating straight and curved apostrophes in the lyrics it hosts to form a type of watermark. Converting the patterns into Morse code reveals the words “Red Handed.” We’ve reached out to Google for comment, but the company told the WSJ that it licenses the content from a third party, LyricFind Inc, and that it takes “data quality and creator rights very seriously and hold our licensing partners accountable to the terms of our agreement.” LyricFind denied that it took the lyrics from Genius.

In a statement to The Verge, a Google spokesperson confirmed that the information in search results are licensed from various sources, and says that the company is “investigating this issue with our data partners and if we find that partners are not upholding good practices we will end our agreements.”

The complaint comes as the US Department of Justice has reportedly been planning to take up an antitrust investigation against Google for its business practices, and as politicians have begun calling for the breakup of the largest tech firms.

Updated June 16th 5:30PM ET: Updated with a statement from Google.