In Bright & Co. v. Holbein Family Mineral Trust, 995 S.W.2d 742 (Tex. App.--San Antonio 1999, pet. denied), a lessor sued a lessee for non-payment of gas royalties for a certain period. The lessee alleged offset as an affirmative defense and counterclaim, asserting it overpaid royalties during another period and was entitled to recoup those overpayments against the amounts sought by the lessor. Id. at 746. The court held that the offset claim was barred because it constituted a counterclaim and was filed outside the limitations period. Id. at 746-47. The court also rejected the lessee's contention that its offset claim constituted an affirmative defense, holding that such claim to recoup certain royalties did not operate to negate the lessor's claim for unpaid royalties for a different time period. See id. at 747.