Conversation so far:
What is the undisputed champion in boxing?
In professional boxing, the undisputed champion of a weight class is the boxer who holds world titles from all four of the major sanctioning organizations simultaneously.
What year did Mike Tyson start the journey of Undisputed heavyweight champion?
In 1987, Mike Tyson began his journey of undisputed heavyweight champion in a match against James Smith.
Who did Mike Tyson fight after James Smith in 1987?
Mike Tyson beat Pinklon Thomas in May by TKO in the sixth round.

Question: What year was that fight?
Self-contained rewrite: What year was the fight between Mike Tyson and Pinklon Thomas?