Wendt appeals from a judgment entered upon a jury verdict of guilty of interstate transportation of a stolen motor vehicle in violation of -18 U.S.C.A. § 2312. We find his contentions that there is insufficient evidence to convict and that the court erroneously failed to give a cautionary instruction contemporaneously with the admission of evidence of a prior conviction to be without merit and affirm.

No motion for a judgment of acquittal was made by Wendt. The question of the sufficiency of the evidence was thus not preserved for appellate review absent a manifest miscarriage of justice. United States v. McGlamory, 5 Cir. 1971, 441 F.2d 130; United States v. Penner, 5 Cir. 1970, 425 F.2d 729. We find none here. On the contrary, the evidence of Wendt's guilt is overwhelming.

Wendt concedes, as he must, that it is proper to impeach the credibility of a defendant by showing prior convictions. United States v. Bland, 5 Cir. 1970, 432 F.2d 96, cert, denied 401 U.S. 912, 91 S.Ct. 877, 27 L.Ed.2d 810; United States v. Justice, 5 Cir. 1970, 431 F.2d 30. He also concedes that no request for a cautionary instruction was made at any time, although such an instruction was given during the court’s charge to the jury. Wendt nevertheless contends that the court’s failure to instruct the jury at the time the testimony was given is plain error. Under the circumstances here shown we dismiss this contention as frivolous.

Affirmed.