Appellants are former employees of the Army and Air Force Exchange Service of the Canal Zone, convicted of conspiracy to defraud the Exchange, an agency of the United States Government, in violation of 18 U.S.C.A. § 371. They now urge reversal of the convictions on the following grounds: (1) the trial court failed to instruct the jury that under C.Z. Code tit. 6, § 42(a) “[a] conviction can not be had on the testimony of an accomplice unless his testimony is corroborated by other evidence which in itself and without the aid of the testimony of the accomplice, tends to connect the defendant with the commission of the offense.”; (2) the trial court abused its discretion in refusing to grant Appellant-Gartlan’s motion for a continuance; (3) Appellant-Thrush-Garces was denied a fair trial because of comments made by the trial judge regarding her proficiency in the English language; (4) the trial court erred in not instructing the jury regarding a hearing, held out of the presence of the jury, concerning Appellant-Thrush-Garces’ proficiency in the English language; (5) there was a substantial variance between the information and the proof adduced at trial.
We have carefully examined the record and find no merit in the last four grounds for reversal urged upon us by Appellants. We turn then to the trial court’s failure to give the proper accomplice instruction under the Canal Zone Code.1 Since Appel*1120lants failed to request an accomplice instruction, we examine the point under the plain error standard of review. Fed.R. Crim.P. 52(a); see United States v. Nabrit, 554 F.2d 247, 248 (5th Cir. 1977).
Generally, in this Circuit a conviction may be based solely on the uncorroborated testimony of an accomplice if the testimony is not incredible or otherwise unsubstantial on its face. United States v. Garner, 581 F.2d 481, 486 n.2 (5th Cir. 1978); United States v. Trevino, 565 F.2d 1317, 1319 (5th Cir.), cert. denied, 435 U.S. 971, 98 S.Ct. 1613, 56 L.Ed.2d 63 (1971); United States v. Kelley, 559 F.2d 399, 400 (5th Cir.), cert. denied, 434 U.S. 1000, 98 S.Ct. 644, 54 L.Ed.2d 497 (1977); Tillery v. United States, 411 F.2d 644, 647 (5th Cir. 1969). While no particular instruction is necessary in such cases, we have emphasized repeatedly the desirability of instructing the jury that accomplice testimony should be scrutinized carefully. E.g., United States v. Beasley, 519 F.2d 233, 241 (5th Cir. 1975), vacated on other grounds, 425 U.S. 956, 96 5. Ct. 1736, 48 L.Ed.2d 201 (1976); Tillery v. United States, 411 F.2d 644, 647 (5th Cir. 1969). Prosecutions under the Canal Zone Code, however, are governed by a different rule. See Fed.R.Crim.P. 54(a). Section 42(a) of the Canal Zone Code, C.Z. Code tit. 6, § 42, explicitly states that the testimony of an accomplice must be corroborated if it is to provide the basis for a conviction. In view of the clear language of this statute, we believe that a jury instruction to that effect is mandatory rather than merely desirable.
In the instant case, the alleged accomplice,2 Maggie Wilson, testified that on occasion she had been requested to under-ring merchandise by Appellant-Gartlan. Additionally, Mrs. Wilson testified to having witnessed several transactions, in which Appellants participated, which indicated their involvement in a scheme to defraud the Exchange. The record also shows that several other witnesses gave testimony concerning the underringing activities of Appellants. Since there was substantial evidence, aside from the testimony of Mrs. Wilson, connecting Appellants with the commission of the offense, we cannot say that the convictions were in any sense based on the uncorroborated testimony of an accomplice.
While we hold that in prosecutions under the Canal Zone Code, where an accomplice testifies against the defendant, it is error not to instruct the jury on the substance of Section 42, in this case the evidence of guilt was so overwhelming that any error committed by the trial court must be considered harmless.
AFFIRMED.