The present case comes before this court on a petition for a writ in the nature of mandamus pursuant to the All Writs Act, 28 U.S.C. § 1651 (1970), and Rule 21, Fed. R. App. P. Petitioners, plaintiffs in Zweibon v. Mitchell, D. D.C. Civil Action No. 2025-71, request this court to review and order reversal of the District Court’s order striking their motion for a jury trial. We find (1) that mandamus is available to remedy deprivation of the right to trial by jury, and (2) that petitioners have not waived their right to demand a jury trial on the issue of the “good faith” of the defendants.
I. BACKGROUND
In October 1971 petitioners (hereinafter “Zweibon”) filed a complaint seeking damages arising from warrantless wiretaps effected by various officials and employees of the United States Government, including the Attorney General. The wiretapping, according to Zweibon, violated both constitutional and statutory provisions, and the demand for recovery of money damages was premised on both an implied cause of action analogous to that recognized in Bivens v. Six Unknown Named Agents of Federal Bureau of Narcotics, 403 U.S. 388, 91 S.Ct. 1999, 29 L.Ed.2d 619 (1971), and a cause of action expressly created by Title III of the Omnibus Crime Control Act of 1968, 18 U.S.C. §§ 2510-2520 (1970). The complaint did not include a demand for a jury trial.
In their answer filed July 28, 1972 the defendants (hereinafter “Mitchell”) set forth several defenses, among which was a claimed unqualified immunity from civil liability for “foreign security” wiretaps undertaken by federal officials pursuant to a presidential directive. Mitchell, however, failed to expressly plead “good faith” as a defense.1 The first mention of “good faith” as a defense occurred in Mitchell’s opposition to Zweibon’s motion for partial summary judgment and his cross-motion for summary judgment.2 Zweibon responded to the issues raised in the opposition and cross-motion for summary judgment, including *170the issue of “good faith,” without objecting that the issue had not been presented fairly by Mitchell’s answer.3 No demand for a jury trial was endorsed on any of the papers filed by either Zweibon or Mitchell.
Without reaching the issue of “good faith” the District Court granted Mitchell’s cross-motion for summary judgment, ruling, in substance, that the wiretaps were legal and, therefore, recovery was barred. Zweibon v. Mitchell, 363 F.Supp. 936 (D. D. C. 1973).4 On appeal, this court en banc held, inter alia: (1) that presidential authority to wiretap without prior judicial review did not extend to the circumstances presented by Zweibon; (2) that recovery could be premised on both constitutional and statutory grounds; (3) that a “good faith” defense could be interposed to both the statutory and constitutional causes of action;5 and (4) that on remand the District Court should take evidence on and make the initial determination concerning this affirmative defense. Zweibon v. Mitchell, 170 U.S.App.D.C. 1, 14 n.18, 78 n.274, 516 F.2d 594, 607 n.18, 671 n.274 (1975) (en banc) (plurality opinion). The opinion of this court was filed June 23, 1975, as was the judgment of this court reversing the District Court’s order of summary judgment.
Following denial of motions for rehearing en banc, the mandate of this court was returned to the District Court September 8, 1975.6 Nine days later Zweibon filed a demand for a jury trial of all issues. Mitchell then moved to strike the demand. No action on the demand was taken by the District Court until a calendar call hearing on March 2, 1977, during which the demand was orally renewed by Zweibon’s counsel but was stricken by order of the District Court.7 The pending petition seeking review of this order was then filed.
II. REVIEW ON MANDAMUS
In the opposition to the petition filed in behalf of respondent, Judge Pratt,8 the Government argues that mandamus is not available to review the order of a District Court refusing a jury trial where the case presents only legal (as opposed to a combination of legal and equitable) issues. In support of this proposition respondent relies on several general principles governing interlocutory review of District Court orders and the availability of mandamus, but fails to cite a single precedent which expressly adheres to this proposition. Rather, we find that, where denial of trial by a jury is alleged to be improper, the claimed factual and legal bases for denial may be reviewed on mandamus, whether the complaint presents only issues triable at law or issues triable both at equity and at law. Bereslavsky v. Caffey, 161 F.2d 499 (2d Cir.), cert. denied, 332 U.S. 770, 68 S.Ct. 82, 92 L.Ed. 355 (1947)(amended complaint raised only issues triable at law; mandamus issued); see Beacon Theatres, Inc. v. Westover, 359 U.S. 500, 511 & n.20, 79 S.Ct. 948, 957, 3 L.Ed.2d 988 (1959) (citing Bereslav*171sky, supra, to support conclusion, “we think the right to grant mandamus to require jury trial where it has been improperly denied is settled”). We therefore conclude that this denial of a jury trial may be reviewed on a petition for a writ in the nature of mandamus.
III. ISSUANCE OF THE WRIT
Whether the writ should issue, however, is a more difficult question. We start our analysis by noting that, in the context of this case, the procedural rules with which we must deal9 relate to assertion of a right assured by the Constitution.10 These procedural rules are not intended to diminish this right, see Kimberly-Clark Corp. v. Kleenize Chemical Corp., 194 F.Supp. 876, 879 (N.D.Ga. 1961), and should be interpreted, where possible, to avoid giving effect to dubious waivers of rights. Schaefer v. Gunzberg, 246 F.2d 11, 15 (9th Cir.), cert. denied, 355 U.S. 831, 78 S.Ct. 45, 2 L.Ed.2d 43 (1957); 5 J. Moore, Federal Practice ¶ 38.43 at 336.2 (2d ed. 1976).
Under Rule 38(b) & (d), Fed. R. Civ. P.,11 a party may demand trial by jury of any issues which are triable to a jury as a matter of right.12 The right, however, is waived as to any issue to which a demand is not served prior to or within 10 days after service of the last pleading directed to such issue.13 In assessing respondent s claim that the right to demand a jury trial has been waived, therefore, it is necessary to determine when the last pleading directed to the issue of “good faith” was served.14 Respondent argues that the issue of “good faith” was first raised implicitly in Mitchell’s answer filed in 1972 when the claimed unqualified official immunity was pleaded.15 He also argues that the issue was expressly injected into the case by Mitchell’s cross-motion for summary judgment and that this was recognized as such by Zweibon when he responded to this issue in his opposition to the cross-motion. In either event, respondent argues, the last pleading directed to the issue of “good faith” was served years before Zweibon’s jury demand. It is on these alternative bases that he would have us hold that the right to trial by jury has been waived.
We conclude, however, that neither argument justifies denial of a jury trial on the issue of good faith. First, as noted in the en banc plurality opinion remanding this case for trial, “good faith” as therein defined is an affirmative defense. Zweibon v. Mitchell, supra, 170 U.S.App.D.C. at 14 n.18, 516 F.2d at 607 n.18. Under Rule 8(c), Fed. R. Civ. P., all such affirmative defenses must be expressly pleaded. Defendants have recognized that the de*172fense which they did expressly plead in their complaint — unqualified official immunity from civil liability — differs conceptually from their “good faith” defense.16 See Cross-Motion for Summary Judgment filed April 24, 1973, App. 31-38, 39-46. Waiver of the right to a jury trial on an affirmative defense should not be presumed where the defendant has failed to expressly plead the defense in accordance with the rule. See 5 J. Moore, supra, ¶ 38.43 at 336.2. Contrary to respondent’s position, therefore, the affirmative defense of “good faith” was not fully and adequately raised in Mitchell’s answer for purposes of Rule 38(b) & (d).
Second, neither Mitchell’s cross-motion for summary judgment nor Zweibon’s opposition to the cross-motion constitute pleadings which would trigger the 10-day period for demanding trial by jury of any new issues raised therein. See Molinaro v. Watkins-Johnson CEI Division, 359 F.Supp. 467 (D.Md.1973) (opposition to summary judgment held not “pleading directed at the issue” for purposes of Rule 38); Rule 7(a), Fed. R. Civ. P.17 (indicating motions for summary judgment are not included in definition of “pleading”); cf. Dasho v. Susquehanna Corp., 461 F.2d 11, 21-23 (7th Cir.), cert. denied, 408 U.S. 925, 92 S.Ct. 2496, 33 L.Ed.2d 336 (1972).
Insofar as these Rules impose time barriers, their warning signals must be read in terms of the Rules’ own definitions and underlying concepts; in these terms the Rules clearly distinguish between a “pleading” and a motion, and a time limit based on a “pleading” does not fairly alert counsel that time runs from the filing of a motion. In terms of the purpose of Rule 38(a), it is meaningful to require a demand for jury trial promptly after the last pleading contemplating a trial, while it is not meaningful to provide that procedures as to how the trial shall be conducted shall be triggered by a motion that seeks a disposition of the controversy without any trial.18
Nevertheless, the issue of “good faith” is now before the District Court because under Rule 15, Fed. R. Civ. P.19 the pleadings are properly treated as amended pursuant to this court’s opinion and judgment of reversal to include this issue.20 Such an *173amendment of the pleadings, through which an issue is raised for the first time, triggers the 10-day period for demand of trial by jury of that issue. See Land v. Roper Corp., 531 F.2d 445, 450 (10th Cir. 1976); Hostrop v. Board of Trustees of College Dist. No. 515, 523 F.2d 569, 580 (7th Cir. 1975), cert. denied, 425 U.S. 963, 96 S.Ct. 1748, 48 L.Ed.2d 208 (1976); 5 J. Moore supra, ¶ 38.39[2] at 322. Therefore, the timeliness of Zweibon’s jury demand should be measured from the effective date of this court’s judgment by which the pleadings were amended, namely the date of the return of this court’s mandate to the District Court. Since Zweibon’s demand was filed within 10 days following return of the mandate, it constituted a timely exercise of the right to trial by jury of the “good faith” issue and should not have been struck.
IY. CONCLUSION
In view of the above, we assume that on remand the District Court will provide Zweibon with a jury trial of the factual issues relating to the affirmative defense of “good faith” as defined by this court in its en banc decision in Zweibon v. Mitchell, supra. Thus it is unnecessary to issue the writ of mandamus at this time.
Remanded.