"For the 'River to River' festival in Florence recently, the choice of the opening film was Black. I sat through it, and at every fault that I discovered in my work, I looked about to see if those that saw it with me saw it too...," the 70-year-old posted on his blog srbachchan.tumblr.com.
"The error that you notice remains, and bothers ... but alas nothing can be done with it," he further posted.
Directed by Sanjay Leela Bhansali, Black revolves around a visual and hearing impaired girl, played by Rani Mukherji, and her relationship with her teacher, played by Big B, who later develops Alzheimer's.
"I made a horrible error on the dining table scene in Black and it haunts me till today. Though I am certain if asked none of you would be able to find out. Would you," wrote 70-year-old star, who played teacher Debraj Sahay in the film.
"Let us test your judgement! It's the dining table scene, when the younger sister to Rani, announces her engagement, and Rani's letter to her sister with whom she has a traditional sister-sister jealousy-cum-envy relation, gets up to give her speech and then Rani's letter to her elder sister is read by Mr Sahay ... ! What was the wrong that you noticed in my performance there??
"Love luck and happy viewing of Black again for the fault finding," Big B further posted.