A day after his social media company went public, Facebook co-founder and chief executive Mark Zuckerberg married his longtime girlfriend Priscilla Chan on Saturday.

The couple, who met at Harvard and have been together for nine years, tied the knot in a small ceremony at Zuckerberg’s house in Palo Alto, California, in front of less than 100 guests, who thought they were attending a party to celebrate Priscilla‘s graduation from UC San Francisco’s medical school.

The news was announced on Facebook. “Mark added a life event to May 19, 2012 on his timeline: Married Priscilla Chan,” the page’s activity feed said.  Mark Zuckerberg, posted a simple wedding photograph, showing the couple against a backdrop of plants and small lights on a string.