Groups with normal restriction property

Let G be a finite group. A subgroup M of G is said to be an NR-subgroup if, whenever K (sic) M, then K-G boolean AND M = K where K-G is the normal closure of K in G. Using the Classification of Finite Simple Groups, we prove that if every maximal subgroup of G is an NR-subgroup then G is solvable. This gives a positive answer to a conjecture posed in Berkovich (Houston J. Math. 24 (1998), 631-638).