The US Customs and Border Protection wants to begin asking Chinese visitors to voluntarily disclose their social media handles when they enter the country. The agency has entered a proposal earlier this week to be published in the Federal Register detailing some changes to the electronic visa system used to vet visitors.

The proposal calls for the Department of Homeland Security to add an additional question to the existing Electronic Visa Update System (EVUS): “Please enter information associated with your online presence – Provider/Platform – Social media identifier.” The question would be optional, but would be used to help screen those who apply for a visa to the United States as needed. The proposal notes that it would affect roughly 3.6 million applicants. According to Politico, the agency hasn’t stated which social media networks would be included on the form.

EVUS is an online system used by Chinese nationals “holding a 10-year B1/B2, B1 or B2 (visitor) visa periodically to update basic biographic information to facilitate their travel to the United States.” DHS notes that the system makes it easier to screen visitors, and that the question would help with that process.

This isn't the first time that the CBP has looked into traveler's social media profiles. In June, a similar system was proposed for the visa waiver program, applicable to many European and Canadian visitors. The system was ultimately put in place later that year. Customs has also become aggressive at asking for the accounts in person, and the Trump administration has discussed the possibility of making the disclosure of such information mandatory.

The proposal will be published on Tuesday, February 21st, and the public has 60 days to comment on the new proposal before it will be formally considered. Comments can be mailed to Customs and Border Protection at its Washington office.