On Dec. 8, Whiting Petroleum Corp. (NYSE: WLL) sewed up its $6 billion acquisition of Kodiak Oil & Gas Corp., making Whiting the de facto big boy on the Bakken/Three Forks block.

While the deal is done, the paying isn’t. Whiting upped its borrowing base by $1 billion on Dec. 22 out of caution that some of Kodiak’s bonds might require repayment. While Whiting bought Kodiak through an all-stock transaction, Kodiak carried with it some significant debt: $1.55 billion of unsecured bonds.

Whiting’s Dec. 22 Securities and Exchange Commission filings noted that the merger means a “change of control” for Kodiak’s debt. That entitles the holder of each outstanding Kodiak note to force Kodiak to make an offer to repurchase its borrowings at a cash value of 101% of the principal amount, plus accrued and unpaid interest.

“After the recent oil and related equity sell-off following the OPEC meeting on Nov. 27, these bonds have traded down to below the put price of 101%,” said Eric H. Otto, analyst, CLSA Americas. “Given the elevated levels of risk in the sector, bondholders may choose to exercise their put option even if bonds trade up such that the put is marginally out-of-the-money.”

Whiting’s amended credit facility pushes its borrowing base to $3.5 billion from $2.5 billion, said Pavel Molchanov, analyst, Raymond James.

“We project fourth-quarter 2014 bank debt of about $1 billion, resulting in a borrowing base utilization of about 30%,” Molchanov said. “Bottom line: while not unexpected, this is a prudent step for the company to take, providing additional liquidity to weather current commodity weakness.”

Whiting and subsidiary Whiting Oil and Gas entered into an agreement with their lenders to increase the amount the company may borrow under its revolving credit facility.