The 33-year-old took to micro-blogging site Twitter to share his apprehensions over his character in the film and posted a link of script's photograph.
"Scariest part I have played yet have no clue how I'm going to get it right. Wish me luck guys," he tweeted.
Directed by Abhishek Chaubey, the film will reunite actress Kareena Kapoor and Shahid after their break-up in 2007. The film also features Alia Bhatt.
Shahid and Kareena dated for more than four years. Together, they worked in films like "Fida", "36 China Town", "Milenge Milenge" and "Chup Chup Ke", out of which most of them fizzled out at the box-office.
Imtiaz Ali's "Jab We Met" was the only movie that turned out to be a runaway success.
