Vertex-coloring graphs with 4-edge-weightings

An edge-weighting of a graph is called vertex-coloring if the weighted degrees yield a proper vertex coloring of the graph. It is conjectured that for every graph without isolated edge, a vertex-coloring edge-weighting with the set {1,2,3} exists. In this note, we show that the statement is true for the weight set {1,2,3,4}.