The Dunn--Lurie additivity theorem states that an algebra with n compatible multiplications is the same as an algebra over the operad of little n-disks, i.e. an En-algebra. I will describe a similar statement for shifted Poisson algebras. Namely, an En-algebra in the category of m-shifted Poisson algebras is the same as an (n+m)-shifted Poisson algebra. I will explain motivitations for such a result coming from mathematical physics and derived Poisson geometry.