Perhaps Matulović's most notorious transgression was against István Bilek at the Sousse Interzonal in 1967. He played a losing move but then took it back after saying "j'adoube" ("I adjust" – spoken before adjusting pieces on their square, see touch-move rule). His opponent complained to the arbiter but the move was allowed to stand. This incident earned Matulović the nickname "J'adoubovic". This reportedly happened several times, including in a game against Bobby Fischer.