The long-range operators for Hartree-Fock exchange from two recently proposed long-range corrected hybrid functionals, omega B97 and omega B97X [J.-D. Chai, M. Head-Gordon, J. Chem. Phys. 128 (2008) 084106], are discussed. A conserved property is found in the middle-range region of the operator from omega B97X. We argue that the. ne details of the Hartree-Fock exchange mixing in this region are responsible for the accuracy of the long-range corrected hybrid functionals in thermochemistry and barrier heights. Published by Elsevier B.V.