A senior Federal Reserve policymaker said Monday it may be impossible to test new measures to limit systemic risk in the banking system before the next financial crisis.

St. Louis Fed President James Bullard said the credibility of too-big-to-fail elements in the sweeping financial reform bill rested on them being tested in practice.

Bullard said it is unclear, but he doesn’t believe such a challenge may happen before another crisis arrives to test efforts to prevent problems at large financial institutions spreading through the broader economy.

He also said uncertainty surrounding the rule-making associated with the reform bill was affecting economic decisions.

Bullard did not address economic policy during his opening remarks at a conference on banking regulation held in St Louis.