Six years after the financial crisis Citigroup has failed a stress test by the Federal Reserve. Citigroup’s capital plan included a quintupling of its dividend but Fed regulators wanted the Too Big To Fail bank to hold onto more capital.

The Fed noted that Citigroup had “multiple deficiencies” in how Citigroup projected potential losses and that the central bank had no choice but to object to Citigroup’s capital plan. “Taken in isolation, each of the deficiencies would not have been deemed critical enough to warrant an objection, but when viewed together, they raise sufficient concerns regarding the overall reliability of Citigroup’s capital planning process.”

This is not the first time the megabank has failed a stress test in the post-crash era.

It’s the second time the Fed has failed one of the bank’s capital plans. The last rejection came in 2012, when Vikram Pandit was the CEO, and the defeat played a role in Pandit’s ouster later that year, a person with knowledge of the board’s discussions said at the time.

While the news was bad for Citigroup, it is a positive sign for a more adversarial relationship between regulators and those they are supposed to be regulating. Contrary to Wall Street’s cultural expectations, regulators are supposed to be challenging the banksters. Previously the relationship was a mutual appreciation society with a revolving door attached between regulators and bankers. Now, hopefully, that culture is changing.

Another factor in Citigroup’s rejection besides being overly optimistic on potential loses was its fiasco in Mexico that cost the firm $400 million. Though the Fed is not reported to have noted the issue as a reason why it objected.

The Fed made no mention of the bank’s discovery of a $400 million loan fraud last month at its Mexico unit, which had stirred speculation that regulators might fault Citigroup’s controls. Corbat has vowed that the people involved will be held accountable.

Though the scandal went unmentioned it certainly would point to Citigroup not being the most vigilant in protecting its assets. Pollyanna doesn’t belong in risk management.

Hopefully this is the beginning not the end of federal regulators challenging Wall Street’s euphoric projections in favor of sound numbers. Banking should be boring.