Neutron capture by a sample enriched in 41K and by a natural potassium sample (93.26% 39K) was measured at the Oak Ridge Electron Linear Accelerator as a function of neutron time of flight over a 40-m flight path. Resonance peaks were fitted by a least-squares fitting program to obtain Breit-Wigner resonance parameters. The energy range extended to all resonances below 153 keV. Corresponding average capture at a temperature typical of stars, kT = 30 keV, is calculated as (11.8 ± 0.4) mb for 39K and (22.0 ± 0.7) mb for 41K.