Appellant-employee, a blind Mexican-American, sued in the district court alleging that he was fired because of his national origin in violation of the Civil Rights Acts of 1964, 42 U.S.C. § 2000e et seq., and 1870, 42 U.S.C. § 1981. The district judge referred the case to a United States Magistrate for trial on the merits with directions to submit proposed findings of fact and conclusions of law. 28 U.S.C. § 636. After hearing testimony and argument of counsel, the magistrate found that the employee had not been fired, but had resigned and that the termination of his employment was not the result of discrimination by his employer, Waco Lighthouse for the Blind. The district court adopted the magistrate’s findings. The employee raises numerous issues in this appeal. We do not reach the substantive issues because the district judge failed to make a “de novo determination” of the objected to portions of the magistrate’s proposed findings as required by statute. Id. Accordingly, the judgment of the district court is reversed and the case is remanded for further proceedings.
A threshold issue is whether the employee consented to referral to the magistrate. The district judge informed the parties, sua sponte, that he was referring the case to the magistrate for trial on the merits. No objection was voiced before the district court or the magistrate or in the briefs in this appeal. Appellant’s counsel belatedly objected to the referral during oral argument. There is case law in other circuits holding that consent is, or may be, a necessary prerequisite to district court referral of a civil case to a magistrate for trial on the merits. Banks v. United States, 614 F.2d 95, 97 (6th Cir. 1980); Muhich v. Allen, 603 F.2d 1247, 1251-52 (7th Cir. 1979); Hill v. Jenkins, 603 F.2d 1256, 1258 (7th Cir. 1979); DeCosta v. Columbia Broadcasting System, Inc., 520 F.2d 499, 504-05 (1st Cir. 1975). The 1979 amendments to § 636 and the relevant legislative history reveal a similar Congressional concern that consent of the parties may be necessary prior to referral of a case to a magistrate for trial on the merits.1
*354We do not reach the difficult issue of whether a nonconsensual referral to a magistrate for trial of a civil case on the merits violates the statute or the Constitution because we find appellant consented to the referral. In Cruz v. Hauck, 515 F.2d 322 (5th Cir. 1975), cert. denied, 424 U.S. 917, 96 S.Ct. 1118, 47 L.Ed.2d 322, a prisoner civil rights action referred to a magistrate under Rule 53(a) of the Federal Rules of Civil Procedure, we held that an appellant who objects to reference to a magistrate for the first time on appeal waives the right. Id. at 331. That holding applies here.
Subsection (b) of 28 U.S.C. § 6362 is the 1976 expansion of magistrate powers. The subsection explicitly permits a district judge to refer non-dispositive pretrial matters to a magistrate for determination. Id., § 636(b)(1)(A). That determination is subject to a “clearly erroneous or contrary to law” standard of review by the district court. Id. The statute also permits the district court to refer dispositive pretrial matters and matters for evidentiary hear*355ing to a magistrate for submission of proposed findings of fact and conclusions of law, but the district judge must make a “de novo determination” of any objected to portions of the magistrate’s proposed findings. 28 U.S.C. § 6S6(b)(1)(BHC). Although the statute (prior to the 1979 amendments) does not explicitly provide for referral of a civil case to a magistrate for trial on the merits, subsection (b)(3) broadly provides that: “[a] magistrate may be assigned such additional duties as are not inconsistent with the Constitution and laws of the United States.” 28 U.S.C. § 636(b)(3). That provision has been interpreted by other circuits to permit consensual reference to a magistrate for trial on the merits in civil rights cases and others. Muhich v. Allen, supra, 603 F.2d at 1251-52 (consensual reference of jury trial of civil rights action to magistrate does not violate the statute or the Constitution); Hill v. Jenkins, supra, 603 F.2d at 1258 (reference for trial on the merits of prisoner civil rights action is permissible, but not without consent of the parties); DeCosta v. Columbia Broadcasting System, Inc., supra, 520 F.2d at 503. We find that consensual references to a magistrate for trial on the merits were permitted under subsection (b)(3) independent of Rule 53 of the Federal Rules of Civil Procedure and subsection (b)(2) (permitting appointment of a magistrate as a special master) even before the 1979 amendments to the statute.3
Since the reference in the instant case was under § 636(b)(3), and not an appointment of a special master under § 636(b)(2), the standard of appropriate district court review of the magistrate s findings was not necessarily the Rule 53(e)(4) standard. Fed. R.Civ.P. 53(e)(4). However, the First Circuit Court of Appeals has held that district court review of a magistrate’s findings after reference for trial on the merits is the Rule 53 standard. DeCosta v. Columbia Broadcasting System, Inc., supra, 509 F.2d at 508.4 That is, findings of fact are final, subject to the clearly erroneous rule; legal rulings are freely reviewable. Fed.R.Civ.P. 53(e)(4). But the Seventh Circuit Court of Appeals has held that the district court must make a de novo determination of the objected to portions of a magistrate’s proposed findings where the referral was for a civil trial on the merits pursuant to § 636(b)(3). Hill v. Jenkins, supra, 603 F.2d at 1258. We agree with the Seventh Circuit. As stated previously, § 636(b) made nondispositive matters subject to “clearly erroneous or contrary to law” review by the district court. 28 U.S.C. § 636(b)(1)(A). The statute requires the district court to make a “de novo determination” of the enumerated dispositive matters which are referred to the magistrate under § 636(b). A civil trial on the merits is certainly a dispositive matter. Accordingly, we infer that any power to refer dispositive matters under § 636(b)(3) carries with it a requirement of “de novo determination” by the district judge of the portions of the magistrate’s findings to which a party objects.
Even though the district judge’s order stated that he had “made an independent review of the record”, we find that there was no “de novo determination” of *356the contested portions of the magistrate’s findings as required by 28 U.S.C. § 636(b)(1)(C). There is no indication in the record that the district court reviewed the testimony of the witnesses. The transcript of the proceedings before the magistrate was prepared two months after the district court order, and the record is silent as to any tape recording of those proceedings. The Supreme Court has recently held, in a criminal suppression hearing case referred to a magistrate under § 636(b)(1)(B), that the district court is not required to conduct a de novo hearing of the witness concerning credibility matters that a party objects to, at least if the district judge accepts the credibility findings of the magistrate. United States v. Raddatz, - U.S. - n.7, 100 S.Ct. 2406 n.7, 65 L.Ed.2d 424 (1980). It follows that the district court in this civil case was not required to conduct a de novo examination of the witnesses. However he was required to make a “de novo determination” of the contested findings. 28 U.S.C. § 636(b)(1)(C). The decisions of the magistrate were decisions on the credibility of the various witnesses. A district court cannot make a “de novo determination” of the credibility of a witness without at least reading a transcript or listening to a tape recording of the testimony of the witness. Accord, Hill v. Jenkins, supra, 603 F.2d at 1259. Cf. United States v. Marshall, 609 F.2d 152, 155 (5th Cir. 1980) (holding that a district judge errs by rejecting the credibility findings of the magistrate without at least consulting the transcript of the proceedings before the magistrate).
We reverse and reman'd. The district court is directed to review the transcript of the proceedings before the magistrate and make a “de novo determination” of the magistrate’s findings. If the district judge determines that the magistrate’s findings are erroneous, then, prior to entry of an order rejecting the magistrate’s findings, he must further determine if it is necessary to conduct a new hearing at which he can observe the demeanor of the witnesses. In that regard the district court’s attention is directed to United States v. Raddatz, supra, - U.S. at - n.7, 100 S.Ct. at 2415 n.7, 65 L.Ed.2d 424 and United States v. Marshall, supra, 609 F.2d at 155.
REVERSED AND REMANDED WITH INSTRUCTIONS.