Credit-default swaps market leaders will meet this week in New York and London to discuss changes to the contracts in what may be the biggest revisions since 2009, according to people familiar with the situation.

Possible changes to standard contracts, which are governed by the International Swaps and Derivatives Association, include how debt-for-equity exchanges would be treated after a bankruptcy, specifying that credit swaps only cover losses from defaults that occur after their purchase, and clarifying how the date of a so-called credit event is determined, said the people, who asked not to be named because the discussions are private.

ISDA's credit steering committee is considering the changes after Greece's debt restructuring posed the biggest test for the $26.5 trillion credit swaps market since banks including JPMorgan Chase & Co. created it more than a decade ago. ISDA, based in New York, last overhauled the derivatives three years ago in the so-called Big Bang and Small Bang protocols that created a new set of standards to increase transparency and confidence in the market.