Because the landlord had in her possession on September 1,1978, security *984deposits of the plaintiffs, the provisions of G. L. c. 186, § 15B, as appearing in St. 1978, c. 553, § § 2-3, applied in regard to the enhanced penalties for wrongful detention of security deposits. Friedman v. Costello, 10 Mass. App. Ct. 931 (1980). The defendant’s claim that the statute was unconstitutional because of its retroactive effect is without merit where the defendant’s obligation to return the security deposits in a proper manner materialized on June 20,1979, some ten months after the statute went into effect.

Judgment affirmed.