Let S be a set of integers. A graph G is said to have the S-property if there exists an S-edge-weighting w:E(G)→S such that any two adjacent vertices have different sums of incident edge-weights. In this paper we characterise all bridgeless bipartite graphs and all trees without the {0,1}-property. In particular this problem belongs to P for these graphs while it is NP-complete for all graphs.