A composition comprises 5-15 wt % of the potassium salt of 1,2-benzisothiazolin-3-one (K-BIT) calculated as 1,2-benzisothiazolin-3-one (BIT), 2-12 wt % of a nonionic surfactant, and at least 70 wt %. The presence of the nonionic surfactant stabilizes an aqueous solution of the composition at a temperature of −5° C. A method of stabilizing an aqueous solution comprising 5-15 wt % of the potassium salt of 1,2-benzisothiazolin-3-one (K-BIT) calculated as 1,2-benzisothiazolin-3-one (BIT) and at least 70 wt % water at a temperature of −5° C., includes the step of incorporating within the aqueous solution an amount of the nonionic surfactant so that the aqueous solution has 2-12 wt % of the nonionic surfactant.
