Google says it has blocked several terms associated with hate speech from being used as ad keywords on YouTube videos.

The move follows a report by The Markup, which found that advertisers could search for terms like “white lives matter” and “white power” when deciding where to place ads on YouTube:

Google offered advertisers hundreds of millions of choices for YouTube videos and channels related to White supremacist and other hate terms when we began our investigation, including “all lives matter”—a phrase frequently used as a dismissive rejoinder to Black Lives Matter—and “White lives matter”—which the Southern Poverty Law Center describes as both a neo-Nazi group and “a racist response to the civil rights movement Black Lives Matter.”

At the same time, The Markup found, Google was blocking advertisers from using terms such as “Black Lives Matter” to find videos and channels to run ads against. After The Markup reached out to YouTube parent company Google for comment, it says the company actually blocked more racial and social justice terms, including “Black excellence” and “civil rights.”

“We take the issue of hate and harassment very seriously and condemn it in the strongest terms possible,” a Google spokesperson said in an email to The Verge. “Though no ads ever ran against this content on YouTube, because our multi-layered enforcement strategy worked during this investigation, we fully acknowledge that the terms identified are offensive and harmful and should not have been searchable. Our teams have addressed the issue and blocked terms that violate our enforcement policies. We will continue to be vigilant in this regard.”

YouTube says it has several layers of protection in place to prevent offensive or harmful ads from running on its platform, and that it regularly removes videos containing hate speech. Last year, the company says it blocked or removed more than 867 million ads for trying to evade its detection systems and more than 3 billion bad ads in total.

Google says it does not publicly disclose how it develops its enforcement tools, so that so-called bad actors can’t circumvent its rules.

YouTube has battled hate speech on its platform for several years, with mixed results. In 2019, it banned white supremacist content, and the company said it would restrict channels from monetizing videos that “repeatedly brush up against our hate speech policies,” preventing them from running ads.

In a blog post last June, YouTube CEO Susan Wojcicki said the company’s hate speech policy “specifically bans videos alleging that a group is superior based on qualities like race, gender, religion, or sexual orientation in order to justify discrimination, segregation or exclusion.”