Cohomology theories with supports

For $E$ a presheaf of spectra on the category of smooth $k$-schemes satisfying Nisnevich excision, we prove that the canonical map from the algebraic singular complex of the theory $E$ with quasi-finite supports to the theory $E$ with supports intersecting all the faces properly is a weak equivalence on smooth $k$-schemes that are affine or projective. This establishes some cases of a conjecture of Marc Levine.