This is an appeal from a judgment entered in the United States District Court for the Southern District of New York, Sand, J., on October 24, 1990, granting the defendant insurers’ motions for partial summary judgment on Counts Four and Seven of Olin Corporation’s (Olin) complaint. The district court ordered that final judgment be entered on these two counts pursuant to Fed.R.Civ.P. 54(b).

Olin initiated this action against several insurers from which it had purchased primary or excess comprehensive general liability coverage. In Counts Four and Seven, Olin sought a declaration that these insurers were obligated to indemnify it for any liabilities stemming from mercury contamination that occurred at the site of Olin’s plant in Saltville, Virginia. The defendant insurers moved for summary judgment on these counts, arguing that New *64York law controlled and that Olin had failed to provide them with timely notice of the potential claims relating to the Saltville contamination.

In a careful and thorough opinion, Judge Sand held that all of the insurance policies at issue were controlled by New York law and concluded that Olin had failed to notify any of its insurers in a timely fashion. Judge Sand, therefore, granted the defendants’ motions for partial summary judgment. We conclude that the district court properly chose to apply New York law to the insurance contracts and that it correctly held as a matter of law that Olin failed to provide all its insurers with timely notice of occurrence. Finally, we reject Olin’s invitation to certify to the New York Court of Appeals the question of whether an insurer must demonstrate actual prejudice resulting from late notice in the context of environmental contamination claims. Certification is warranted only when applicable state law is unclear or nonexistent. See Retail Software Services, Inc. v. Lashlee, 838 F.2d 661, 662 (2d Cir. 1988). There is abundant New York precedent establishing that an insurer need not demonstrate prejudice when a late notice defense is advanced. We recently recognized this well established principle of New York law. See Ogden Corp. v. Travelers Indemnity Co., 924 F.2d 39, 42-43 (2d Cir. 1991). Accordingly, we affirm substantially for the reasons stated by Judge Sand in his opinion dated August 2, 1990. See Olin Corp. v. Insurance Co. of North America, 743 F.Supp. 1044 (S.D.N.Y. 1990).

Judgment affirmed.