We give a necessary and sufficient condition for the existence of a positive principal eigenvalue for a periodic-parabolic problem with indefinite weight function. The condition was originally established by Beltramo and Hess [extit{frenchspacing Comm. Part. https://www.bekindtopets.com/best-offer-Bilstein-53-264817-B8-5100-Series-Dual-Steering-Damper-Kit-2013-2022-Ram-2500-3500-super-value/