Supernova remnants have long been suspected of accelerating cosmic ray protons, but unambiguous proof is still lacking. One clear prediction of this scenario is the existence of a low-energy (pion-bump) cutoff in the spectra of hadronically produced gamma rays at 67MeV. The Fermi LAT provides unprecedented sensitivity in the energy range below 200 MeV and thereby has access to this feature. We present first results of a search for the pion-decay cutoff in bright SNRs with the Fermi LAT.