Under Section 56 of the Indian Contract Act, a contract becomes void when an act which was agreed to be performed becomes impossible or unlawful after the contract is made. This doctrine is known as: 

Section 56 of the Indian Contract Act embodies the doctrine of frustration (also termed supervening impossibility). It provides that a contract to do an act which, after the contract is made, becomes impossible or by reason of some event which the promisor could not prevent, unlawful, becomes void when the act becomes impossible or unlawful. The Supreme Court in Satyabrata Ghose v. Mugneeram Bangur (1954) held that Section 56 is exhaustive of the law of frustration in India, and English doctrines of frustration apply only to the extent they are consistent with this provision. It covers both physical and legal impossibility arising after the formation of the contract.