Mark Zuckerberg sat before the Senate yesterday, taking questions (and comments) from several Senators over Facebook and its use of user data.

While many Senators seemed to have very little idea how Facebook (and perhaps the Internet) even works, Senator Ted Cruz went after Zuckerberg on one of the worst-kept secrets in social media: bias against conservative voices.

During Facebook founder and CEO Mark Zuckerberg’s testimony before CongressTuesday, Sen. Ted Cruz, R-Texas, said he believes many Americans are “deeply concerned” about what he called Facebook’s “pervasive pattern of bias and political censorship.”

The senator cited the 2016 controversy over how Facebook editors handled conservative-leaning political news in the trending topics feature. He also questioned why Facebook shut down certain pages it deems controversial, naming examples such as as “Chick-fil-A appreciation day” page, a post from a Fox News reporter, and Trump supporter Diamond and Silk’s Facebook page.

“Senator, let me say a few things about this. First, I understand where that concern is coming from because Facebook and the tech industry are located in the Silicon Valley which is an extremely left-leaning place,” Zuckerberg said, addressing Cruz. “And this is actually a concern that I have and that I try to route out in the company — is making sure that we don’t have any bias in the work that we do.

Here’s a video of the Cruz-Zuckerberg exchange, courtesy CNN.

Cruz’s line of questioning also comes at a time when Facebook’s recent algorithm changes appear to have had a greater impact on right-leaning news pages. The changes are supposed to make news pages appear less frequently in a person’s timeline, but various outlets have reported that conservative sites are seeing a greater dip in overall traffic from Facebook.

Zuckerberg, for his part, did acknowledge a general left-leaning bias in Silicon Valley, but was it enough?