Plaintiffs, eight named Medicaid recipients, appeal from a summary judgment granted in favor of the Department of Human Services (hereinafter “DHS”) by the Superior Court (Kennebec County, Alexander, J.). Plaintiffs contend that the court erred in finding that certain co-payment rules adopted by DHS are valid and are not arbitrary, capricious, or unlawful. Finding no error, we affirm the judgment.

In 1991 the Legislature directed DHS to require Medicaid recipients to pay part of certain medical services. P.L.1991, ch. 622, § M-11. DHS subsequently issued proposed co-payment rules in January of 1992. DHS published notice of the proposed rules and submitted fact sheets to the Legislature in accord with the Maine Administrative Procedure Act. 5 M.R.S.A. §§ 8053-A, 8064 (Supp. 1992).1 Before the proposed rules took effect, the Legislature repealed its authorization to impose co-payments and enacted a more limited authorization. P.L.1991, ch. 780, § R-9.2 The new authorization differed from the former in that it permitted co-payment rather than requiring it, required co-payment caps or the exclusion of some services from co-payment, and required that co-payment be nominal in amount. DHS again proposed rules and published public notice. Although the proposed rules included new provisions for co-*663payment caps, DHS did not submit a revised fact sheet to the Legislature.

Plaintiffs filed a complaint in the Superi- or Court seeking to enjoin DHS from instituting the co-payment rules on the basis that they were adopted in violation of 5 M.R.S.A. § 8064 (Supp. 1992).3 The Superior Court applied the standard of review prescribed by 5 M.R.S.A. § 8058 (1989)4 and held that the rules were valid because the procedural error, if any, was not substantial and the rule would not have changed significantly in the absence of any error.

Plaintiffs argue that 5 M.R.S.A. § 8064 invalidates the co-payment rules because DHS has no authority to adopt the rules absent compliance with the statute. The DHS co-payment provisions constitute “rules” within the meaning of 5 M.R.S.A. § 8002(9)(A) (1992).5 Consequently, courts must apply the standard of judicial review specified by 5 M.R.S.A. § 8058. See, e.g., Cumberland Farms Northern v. Maine Milk Comm’n, 428 A.2d 869, 873 (Me. 1981) (applying the section 8058 standard of review after adjudging rules setting minimum prices for the sale of milk as rules within the meaning of 5 M.R.S.A. 8002(9)(A)). Section 8058 establishes a harmless error standard similar to that employed in ordinary civil litigation, see M.R.Civ.P. 61,6 and modifies the prohibition set forth in section 8064.

DHS was granted authority by the Legislature to impose co-payments and institute co-payment caps. Any error in the rulemaking process involved in the present case was at most procedural. In amending section 8058 in 1985, the Legislature substituted a reference to procedural invalidity for language referring to improper adoption. P.L.1985, ch. 680, § 6. The accompanying Statement of Fact noted that the amended sections “limit the procedural grounds that automatically invalidate a rule” but that “[violation of those procedures affecting public participation in the rule-making process, or the specific time limits for rulemaking, will still void a rule.” L.D. 2341, Statement of Fact (112th Leg-is. 1985). We conclude that the Legislature intended to narrow the circumstances in which procedural error would automatically *664invalidate a rule. Those circumstances in which invalidation is automatic principally involve a denial of public participation,7 which is distinguishable from the failure to provide a revised legislative fact sheet as in the present case. The Superior Court did not err in finding that any error was procedural, that it was not related to matters of central relevance, and that there was not a substantial likelihood that the rules would have been significantly changed had DHS filed a revised fact sheet with the Legislature.

Plaintiffs also argue that the court erred in finding that the co-payment caps met the requirement that co-payments be “nominal.” Plaintiffs rely on the cumulative impact that the co-payments may have on the recipients of multiple Medicaid services. We conclude, however, that the Superior Court did not err in adopting the DHS interpretation that the Legislature intended only that the caps be nominal relative to the actual cost of the services themselves. The legislative history does not reveal a contrary legislative intent on the meaning of “nominal,” and the federal rules applying a similar restriction do not support plaintiffs’ position even by analogy. See 42 C.F.R. §§ 447.53, 447.54(d) (1992).8

The Superior Court did not err in finding that plaintiffs failed to establish that the co-payment rules are arbitrary, capricious, or unlawful.

The entry is:

Judgment affirmed.

All concurring.