Using an electron monochromator attached to an electron microscope, high energy-resolution electron energy-loss spectra collected from TeO2 have revealed new features in the Oxygen K-edge. Using density-functional theory in the local density and the generalized gradient approximation, we find that core-hole strength of 1.3 gives an excellent fit to our high-resolution experimental data. This indicates that screening is not weak in this oxide, as normally assumed, and that neither the ground state nor a full core-hole model is adequate in quantitative reproduction of the O K-edge in the TeO2 system.