When performance of a contract is substantially impacted by circumstances that could not be foreseen by either party, the law offers a limited range of remedies. Such remedies have come to the forefront of recent legal discussions due to the unexpected impacts of the COVID-19 pandemic and conflict in Ukraine. In civil law jurisdictions, the principle of rebus sic stantibus can effectively change the commercial balance between affected parties. In common law jurisdictions, equitable doctrines of "frustration of contract", "impossibility" and "impracticability" can also rebalance the allocation of commercial risks between parties when a contract is substantially altered by unforeseen circumstances. This session will dive into the dilemma of what may or may not be considered to be unforeseen and will compare the available remedies in civil and common law countries, offering examples based on recent disruptions to international commercial contracts.