The US Treasury just told the market it needs to borrow more than expected. Quite a bit more, actually.

The department revised its net marketable borrowing estimate for the July-September quarter to $739 billion, a jump of $68 billion from what it projected back in May. For the October-December quarter, the Treasury pegged borrowing needs at $628 billion, bringing total second-half borrowing to a combined $1.367 trillion.

What’s behind the revision

The culprit here is pretty straightforward: lower projected cash flows. The government expects to take in less money than previously anticipated, so it needs to issue more debt to cover the gap.

The Treasury started the quarter with a higher cash balance than expected, which offset some of the increased borrowing need. After accounting for that cushion, the net increase narrows to roughly $87 billion.