Rescattering electrons offer great potential as probes of molecular properties on ultrafast timescales. The most famous example is molecular tomography, in which high harmonic spectra of oriented molecules are mapped to "tomographic images" of the relevant molecular orbitals. The accuracy of such reconstructions can be greatly affected by the distortion of scattering wave functions from their asymptotic forms due to interactions with the parent ion. We investigate the validity of the commonly used plane wave approximation in molecular tomography, showing how such distortions affect the resulting orbital reconstructions.