Hair treatment agents include at least one propylene glycol diester and specific polymers based on protein hydrolysates. A composition for the treatment of keratin fibers includes, in a cosmetic carrier, a total of 0.01 to 5.0 wt. %, relative to the entire composition, of at least one propylene glycol diester of formula (I), in which R1 and R2 independently represent a group selected from among at least one linear saturated or unsaturated, branched saturated or unsaturated, and cyclic saturated or unsaturated C6 to C 30 hydrocarbon group and/or a phenyl or a benzyl group optionally substituted with C1 to C4 alkyl groups and/or hydroxy groups and mixtures thereof, and a total of 0.001 to 5.0 wt. %, relative to the entire composition, of at least one polymer, said polymer being composed of at least one protein hydrolysate and at least one silane.
