HONOLULU (KHON) — In an unprecedented move, Twitter fact-checked President Donald Trump.

In an early-morning thread the president tweeted twice about mail-in ballots, claiming they are “substantially fraudulent. Mail boxes will be robbed, ballots will be forged & even illegally printed out & fraudulently signed.”

Twitter added a button underneath the tweet titled “Get the facts about mail-in ballots” which, when clicked, leads to fact-checking links and a “What you need to know” section that states:

“-Trump falsely claimed that mail-in ballots would lead to ‘a Rigged Election.’ However, fact-checkers say there is no evidence that mail-in ballots are linked to voter fraud.
-Trump falsely claimed that California will send mail-in ballots to ‘anyone living in the state, no matter who they are or how they got there.’ In fact, only registered voters will receive ballots.
-Though Trump targeted California, mail-in ballots are already used in some states, including Oregon, Utah and Nebraska.”

Social media companies such as Twitter and Facebook have recently come under fire for having a laissez-faire approach to addressing misinformation.