A fluorine-free composition includes at least one polycarbodiimide compound derived from a carbodiimidization reaction of a carbodiimidization reaction mixture comprising at least one oligomer, wherein the oligomer comprises at least one isocyanate end group and at least two repeating units, wherein each of the at least two repeating units comprises at least one hydrocarbon group having at least 16 carbon atoms. The composition may also include at least one paraffin wax. Such compositions are useful for treating fibrous substrates to enhance their water-repellency.