Winston & Strawn faces a negligence lawsuit filed on Friday in Houston that alleges the firm made drafting errors on documents in an oil and gas deal in 2021 that led to “vicious” litigation that lasted nearly 18 months and resulted in tens of millions in losses.

“The is a case about an oil and gas transaction that went terribly wrong because of the negligent conduct of the law firm hired to negotiate and document it,” plaintiffs Bridgeland Resources and Zargon Acquisition allege in the 51-page petition filed in state district court in Harris County.