New Delhi - Actor Ajay Devgn celebrated his 43rd birthday on the sets of his upcoming film Son of Sardar (SOS). The Singham star was busy shooting for the film in Patiala when fans surprised him by bringing a cake on the sets. On his Twitter page, Devgn said: "Thank u for the lovely Birthday wishes!:) and thanks to the fans that surprised me with a huge cake on #SOS sets, the whole unit enjoyed it!" Son Of Sardar, which also features Juhi Chawla, Sanjay Dutt and Sonakshi Sinha, is directed by Ashwani Dhir.