Ranbir Kapoor is all set to do a cameo in megastar Amitabh Bachchan starrer 'Bhootnath Returns'.

Bachchan, 71, took to Twitter today to express his joy at sharing the screen space with the 'Barfi!' star.

"Ranbir Kapoor on set at 'Bhoothnath Returns', a small cameo for him... Generous of him!," Bachchan tweeted with a picture.

'Bhootnath Returns' is a sequel to the 2008 horror-comedy film 'Bhootnath', which also starred Juhi Chawla and Shah Rukh Khan besides Bachchan as the friendly ghost.

Bachchan also posted on the micro-blogging site that he attended the the premiere of 'Mandela: Long Walk To Freedom' in Mumbai along with South African actors Atandwa Kani and Terry Pheto.

The film starring Idris Elba as Madela chronicles the journey of the anti-apartheid icon.

"Caught up with work and then to be present at the release of film on Mandela .. A moment of reflection starting from 1990..!! Two specific meetings with this great man Nelson Mandela in South Africa! Such humility and dignity to his bearing... Unforgettable," Bachchan tweeted.

Mandela died in December last year at the age of 95.