[UNPUBLISHED]

Iowa inmate Darwin Walden challenges the district court’s 1 adverse grant of summary judgment in his 42 U.S.C. § 1983 retaliatory-discipline action against prison officials. Following careful de novo review, see Johnson v. Hamilton, 452 F.3d 967, 971 (8th Cir. 2006) (standard of re *77 view), we agree with the district court that Walden’s claim failed. Defendants presented evidence that Walden was disciplined for an actual rule violation, and we find nothing indicating that the decision-maker was not impartial. See Hartsfield v. Nichols, 511 F.3d 826, 829, 831 (8th Cir. 2008) (defendant may successfully defend retaliatory-discipline claim by showing “some evidence” that discipline was imposed for actual rule violation; report from correctional officer, even if disputed by inmate and supported by no other evidence, suffices as “some evidence” if violation is found by impartial decisionmaker). Accordingly, we affirm the judgment of the district court. See 8th Cir. R. 47B.