The invention relates to the use of compounds of general formula (I) as crystallization modifiers for organic pigments, in which formula the variables have the following designation: A represents ═N— or ═CH—; X represents methyl or a radical of formula (IIa) if A represents ═N—, and a radical R if A represents ═CH—; Y represents a radical R or a radical of formula (IIb), either X representing a radical of formula (IIa) or Y representing a radical of formula (IIb); and the rings B1 and B2 can be independently substituted, in addition, by at least one of the radicals R which are the same or different and do not represent hydrogen.