At the Large Hadron Collider di-leptonic tt+jets events can be selected with a relatively high signal- to-noise ratio and efficiency, assuming that background events are produced via Standard Model di- agrams. Within the clean sample of these events, both leptons have an opposite electric charge. In several models beyond the Standard Model however, tt+jets topologies which are kinematically similar to the Standard Model tt+jets event topology, are predicted where both leptons have an equal electric charge. The signal of new physics can be diluted by the mis-identification of the electric charge of the leptons in Standard Model tt+jets events. This paper discusses the observability of the excess of same-sign signals above the mis-reconstruction of the Standard Model background. With an integrated luminosity of 30fb-1 , the same-sign signature of pp->tt events with a cross-section larger than 1pb is visible in the measurement of the ratio between same-sign and opposite-sign lepton pair events.