Rate constants for the charge-transfer reactions of Ar+ with O-2 and CO have been measured in a high temperature flowing afterglow from 300 to 1400 K. Comparisons between our results and the previous flow drift tube studies of Dotan and Lindinger at 300 K illustrate the effects of internal excitation on the reactivity. The rate constants measured for both systems agree favorably with the drift tube results from 300 to 900 K. Rotational and translational energy decreases charge transfer equally, consistent with previous experiments, indicating a long-lived collision complex forms during the reaction. The flowing afterglow rate data deviate from the drift tube results above 900 K as a result of populating vibrationally excited states of the neutral reagents. Charge transfer from the thermally populated spin-orbit excited state of Ar+ with O-2 and CO only slightly enhances the rate constants at 1400 K. Populating the upsilon ">0 levels reduces the threshold for accessing excited state products, and the rate constants for vibrationally excited states are much larger than for upsilon "=0. The data suggest most of the enhancement comes from upsilon ">2.