An adhesive sealant composition of at least one moisture-crosslinkable prepolymer and an anti-sagging agent of 5% to 30% by weight of a thixotropic composition of 10% to 40% by weight of a bisurea a) obtained by reaction of a primary aliphatic amine a1) with a diisocyanate a2) having a molar mass of less than 500 g/mol, and 60% to 90% by weight of an ester b) of formula (I): in which R1, R2 and R3 are an oxycarbonylalkyl radical having from 4 to 20 carbon atoms, R4 is hydrogen, methyl or ethyl or —CH2—R5 in which R5 is oxycarbonylalkyl having from 4 to 20 carbon atoms, in the form of a suspension of solid particles of bisurea a) in a continuous phase formed by ester b).