Mumbai - Bollywood superstar Salman Khan has reportedly agreed to do an item number in buddy Ajay Devgans upcoming film Son of Sardar. The friendship of Salman and Ajay is not a new thing as the stars are close friends since the days of Hum Dil de Chuke Sanam. Earlier, Ajay had done a cameo in Salmans Ready and now the Dabang star is paying back by doing an item number for Ajay without charging even a penny for the song. Besides Ajay and Sonakshi Sinha, who are doing the lead roles in the film, Sanjay Dutt and Juhi Chawla are also doing prominent roles in Son of Sardar. A close source said, Salmans nod to the item song has made the Golmaal actor very happy.