A method for making a lithographic printing plate includes the steps of providing a heat-sensitive lithographic printing plate precursor including on a support having a hydrophilic surface or which is provided with a hydrophilic layer, a heat-sensitive coating; image-wise exposing the precursor with IR-radiation or heat; and developing the image-wise exposed precursor with an alkaline developing solution, wherein an anti-sludge agent is present in the precursor or in the developing solution or in the precursor and the developing solution, and wherein the anti-sludge agent is a 5-membered heteroaromatic compound, including —NH— group wherein the hydrogen is capable of being deprotonated in the alkaline developing solution, selected from the group consisting of an optionally substituted benztriazole, 1,2,3-triazole, tetrazole, or indazole compound. According to the above method, the formation of sludge is inhibited or reduced.