The present invention relates to a liquid stabilizer composition A containing (a) at least one liquid sterically hindered amine (HALS) in which the amino group carries a basicity-reducing substituent and which has a molecular weight of at most 1500 g/mol, preferably of at most 1000 g/mol; (b) at least one sterically hindered amine (HALS) having a molecular weight of more than 1500, preferably of at least 1700 g/mol; and (c) at least one liquid UV absorber. The invention relates also to a polymer composition which is in particular a sealant or adhesive composition, comprising at least one silyl-modified polymer and the stabilizer composition A. The invention relates moreover to the use of the stabilizer composition A in a sealant or adhesive composition. Such sealant or adhesive compositions show improved optical properties, also in the finished sealant or adhesive, such as increased clarity and/or reduced haze, and also an improved stability against degradation by heat, light and/or oxygen.