FAIRCHILD, Chief Judge.
Joseph Gratton appeals from his conviction on January 22, 1975 of possession of checks which he knew to have been stolen from the mails, in violation of 18 U.S.C. § 1708.
Gratton challenges his conviction on three grounds. First, he contends that the district court erred in refusing to give his tendered instruction on reasonable doubt, while giving the Government’s tendered instruction which referred to a reasonable doubt as substantial rather than speculative. Since Gratton’s counsel did not object at trial to the instruction now challenged, see Fed. R.Crim.P. 30, our standard of review is whether the challenged instruction constitutes plain error, in accordance with Fed.R.Crim.P. 52(b).
The district court gave the following instruction, LaBuy 6.01-3:
“A ‘reasonable doubt’ means a doubt based on reason and it must be substantial rather than speculative, it must be sufficient to cause you as a reasonably prudent person to hesitate to act in the more important affairs of your life.” (Emphasis added.)
The use of the words “substantial doubt” as equivalent to “reasonable doubt” was found objectionable by this court in United States v. Bridges, 499 F.2d 179, 185-86 (7th Cir. 1974), cert. denied, 419 U.S. 1010, 95 S.Ct. 330, 42 L.Ed.2d 284. See also United States v. Alvero, 470 F.2d 981 (5th Cir. 1972). On the other hand, we approved LaBuy 6.01-3, the instruction at issue here, in dictum in United States v. Lawson, 507 F.2d 433, 440 (7th Cir. 1974), cert. denied, 420 U.S. 1004, 95 S.Ct. 1446, 43 L.Ed.2d 762.
As noted above, however, the issue before us is whether the instruction constituted plain error, and we conclude that it did not. In United States v. Atkins, 487 F.2d 257, 260 (8th Cir. 1973), the Court held that in the absence of a Rule 30 objection, an instruction defining reasonable doubt as substantial doubt was not plain error.
Second, Gratton claims the court erred by refusing to give the following instruction:
“Under the law of Illinois, a person who cashes a check that turns out to have been stolen is civilly liable to the person who cashed the check, and if you find that Mr. Gratton reimbursed the party who cashed any one or more of the checks set forth in the indictment, in whole or in part, you are not to consider that as an admission of guilt.”
Gratton’s defense was that he did not know the checks had been stolen. He brought out testimony that he had made restitution for some of the checks, apparently for the purpose of demonstrating good faith and honesty. The Government did not suggest that the acts of restitution were admissions of guilt.
Defense counsel did not object to the refusal of the instruction in accordance with Fed.R.Crim.P. 30. The mere offer of the instruction does not preserve the error for appeal. If the party whose tendered instruction is refused fails to object to the refusal, stating distinctly the grounds of his objection, the Court of Appeals may review the refusal to instruct only to determine whether it constitutes plain error within the meaning of Fed.R.Crim.P. 52(b). United States v. Lawson, 507 F.2d 433, 443-44 (7th Cir. 1974), cert. denied, 420 U.S. 1004, 95 S.Ct. 1446, 43 L.Ed.2d 762; United States v. Jackson, 477 F.2d 879, 880 (8th Cir. 1973).
Under the circumstances it is doubtful that refusal to give the instruction, peripheral as it was. to Gratton’s defense, would have been deemed reversible error even if the refusal had been fully objected to. It surely does not constitute plain error.
Finally, Gratton contends that the trial court’s refusal to accept a plea of nolo contendere is reversible error. We disagree.
Gratton’s argument is that while the trial judge has broad discretion to accept or reject a nolo plea, he is obligated at