Compensated isocurvature perturbations ( CIPs ) are primordial fluctuations that balance baryon and dark-matter isocurvature to leave the total matter density unperturbed . The effects of CIPs on the cosmic microwave background ( CMB ) anisotropies are similar to those produced by weak lensing of the CMB : smoothing of the power spectrum , and generation of non-Gaussian features . Previous work considered the CIP effects on the CMB power-spectrum but neglected to include the CIP effects on estimates of the lensing potential power spectrum ( though its contribution to the non-Gaussian , connected , part of the CMB trispectrum ) . Here , the CIP contribution to the standard estimator for the lensing potential power-spectrum is derived , and along with the CIP contributions to the CMB power-spectrum , Planck data is used to place limits on the root-mean-square CIP fluctuations on CMB scales , \Delta _ { rms } ^ { 2 } ( R _ { CMB } ) . The resulting constraint of \Delta _ { rms } ^ { 2 } ( R _ { CMB } ) < 4.3 \times 10 ^ { -3 } using this new technique improves on past work by a factor of \sim 3 . We find that for Planck data our constraints almost reach the sensitivity of the optimal CIP estimator . The method presented here is currently the most sensitive probe of the amplitude of a scale-invariant CIP power spectrum placing an upper limit of A _ { CIP } < 0.017 at 95 % CL . Future measurements of the large-scale CMB lensing potential power spectrum could probe CIP amplitudes as low as \Delta _ { rms } ^ { 2 } ( R _ { CMB } ) = 8 \times 10 ^ { -5 } ( A _ { CIP } = 3.2 \times 10 ^ { -4 } ) .