A novel technique with which it is possible to suppress chemical degradation of a compound represented by general formula (1) or a salt thereof in an aqueous liquid formulation containing a compound represented by general formula (1) or a salt thereof. A method for suppressing the generation of a compound represented by general formula (2) or a salt thereof including containing a compound represented by general formula (1) or a salt thereof and a magnesium compound in an aqueous liquid formulation.
