CHARLOTTE, North Carolina (AP) — Two of the nation’s biggest banks — JPMorgan Chase and Citigroup — said Tuesday that their profits improved markedly over the summer, as the U.S. economy tried to bounce back from the coronavirus shutdowns that were imposed earlier this year.

Even so, both banks warned that much uncertainty remains about where the the U.S. economy is headed, and top bank executives bluntly said there is a need for another economic stimulus package to keep the economy from slipping into recession again.

“A good, well-designed stimulus package will simply increase the chance we get better outcomes,” said JPMorgan’s Chairman and CEO Jamie Dimon in an conference call with reporters.

Both Citi and JPMorgan set aside fewer funds to cover potentially bad loans, contributing to the improvement in their third-quarter results. These loan-loss reserves, as they are known, are funds banks put aside when borrowers stop paying on their loans or there are economic signals that show a potential for more loans to go bad.

In the first months of the pandemic, banks set aside tens of billions of dollars to guard against bad loans as state and local economies came to a halt and millions of workers were laid off. Citi itself reserved about $15 billion over the first two quarters of 2020.

But in the third quarter, many cities and states started reopening their economies in phases — restaurants were allowing diners to sit outside and businesses brought limited numbers of workers back to the offices, among other actions. Many economic indicators have markedly improved since the pandemic shutdowns of April and May. For instance, unemployment, albeit still high, is down from historic records earlier in the year.

This has led a good number of investors and economists to predict that — at least economically — the worst is over when it comes to the pandemic.

JPMorgan had $611 million in loan loss provisions this quarter, a fraction of the $10.47 billion the bank set aside in the second quarter. Meanwhile Citigroup’s provision for credit losses was $2.26 billion in the third quarter compared to $7.9 billion the quarter before.

“It is as if Covid-19 never happened,” said Octavio Marenzi, CEO of Opimas, a management consultancy firm, talking about JPMorgan’s loan loss reserves.

But the optimism may be short lived. While Dimon said that if things keep improving, the bank was “over-reserved by $10 billion,” he warned that if the U.S. economy slips back into recession “we are under reserved by $20 billion.” A $30 billion swing in loan-loss reserves is massive for a bank whose quarterly revenue in the third quarter was roughly $29 billion.

JPMorgan reported a profit of $9.44 billion, or $2.92 a share, for the July to September period. That’s up from a profit of $9.08 billion, or $2.68 per share, in the same period a year earlier. The results beat analysts’ expectations for earnings of $2.23 a share, according to FactSet.

Along with fewer loan losses, JPMorgan also had a solid quarter in its investment bank. The division reported profits 52% higher than a year earlier, helped by a surge of revenue from its trading desks.

Citi said its third-quarter net income fell to $3.23 billion from $4.91 billion a year earlier. Per-share earnings for the latest quarter were $1.40. That result topped Wall Street expectations.

JPMorgan and Citi were the first of the major banks to report its results this week. Bank of American and Wells Fargo, the consumer banking giants, will report their results on Wednesday. Investment bank Goldman Sachs will also report its results.