ORDER AND AMENDED OPINION
ORDER
The opinion filed July 9, 2009, 572 F.3d 626, is amended as follows:
Page 629, column 1, line 26, Add a footnote after “Defendants appeal.” stating: “Only an Eighth Amendment outdoor exercise claim is before us on this appeal. We therefore express no view as to the race-based aspect of the lockdowns or any potential Equal Protection claim.”
Page 632, column 2, lines 36-37, Replace “constitution” with “Eighth Amendment”
Page 633, column 1, line 35, Replace “lawful” with “consistent with the Eighth Amendment”
Appellee’s Petition for Panel Rehearing and Rehearing en banc is otherwise denied. See Fed. R.App. P. 35, 40. Judge Thomas would grant the petition.
No further petitions for rehearing or rehearing en banc may be filed.
*1065OPINION
KOZINSKI, Chief Judge:We consider when prison officials may be held liable for depriving inmates of outdoor exercise.
Facts
Gregory Norwood was incarcerated at CSP-Sacramento, a maximum security prison, during a particularly violent period in the prison’s history. Norwood brought this section 1983 action alleging that prison officials violated the Eighth Amendment when they denied him outdoor exercise during four separate extended lockdowns over the course of two years.
The prison initiated these lockdowns after serious inmate assaults on staff. During the lockdowns, inmates were confined to their cells and normal programs were suspended while officials investigated the violence. Based on what they learned, officials gradually eased restrictions on specific gangs, ethnic and racial groups, restoring outdoor exercise sooner for inmates who they believed would pose less risk of further violence. Norwood was not a gang member, but gang members often pressured unaffiliated inmates of the same race or ethnicity to assist them. Prison officials therefore believed that limiting the scope of lockdowns to gang members would be inadequate to ensure safety.
During this two-year period, there were also numerous inmate-on-inmate attacks. Officials did not always initiate total lock-downs after such attacks. According to one defendant, the prison’s response to inmate-on-inmate violence “[djepends on the circumstances of the assault.... [I]f it’s fisticuffs, and it’s a one-on-one situation, no, we wouldn’t lock down for that. If it’s a slashing assault, or a stomping, or multiple inmates involved in a melee, then yes, we would lock down.... ”
Officials initiated the first lockdown in early 2002 after eleven Hispanic inmates attacked four correctional officers, nearly killing one of them. Prison officials didn’t know if the attack was planned or isolated. They also didn’t know, and were never able to ascertain, who provided the weapons. The weeks following the attack brought a series of inmate-on-inmate attacks, including a homicide, as well as another attempted murder of an officer. Officials eventually decided it was safe to begin restoring normal programs, beginning with “critical workers.” Norwood was in the second group of workers to resume outdoor exercise. His exercise had been suspended for about three months.
In early May, a black inmate stabbed an officer in a dining hall. Officials initiated a second lockdown but began restoring normal programs by the end of the month. By mid-July, prisoners other than blacks had resumed outdoor exercise. Even so, attacks on officers occurred during this lockdown, including a battery and an attempted battery. Norwood, who is black, was denied exercise for three months.
In the waning days of 2002, black inmates attempted to murder a correctional officer, and a number of black Crips attacked staff members. Officials initiated a third lockdown, during the course of which inmates committed four batteries or attempted batteries of officers and five batteries or attempted murders of inmates. During this lockdown, Norwood’s outdoor exercise was suspended for four and a half months.
In September of 2003, a black Crip attempted to murder an officer. Because of the seriousness of the incident and the fact that it was the fourth major assault on staff in a 19-month period, officers locked down all inmates and declared a state of emergency. Officers eventually determined that the attacker had acted alone and began restoring outdoor exercise.
*1066But the violence continued. Certain white inmates, and those celled with them, were locked down because of an attempted murder of an inmate in November, and certain Crips and their cellmates remained on lockdown from earlier violence. Norwood was denied outdoor exercise for two months.
A jury found that defendants violated Norwood’s Eighth Amendment right to outdoor exercise but concluded that Nor-wood suffered no harm and thus awarded no compensatory damages. The jury did award $11 in nominal damages and $39,000 in punitive damages. The district court awarded $23,875.55 in attorney’s fees. Defendants appeal.1
Analysis
I
Defendants claim the district court erred by refusing to give the following jury instruction:
In considering whether defendants were deliberately indifferent to the need for outdoor exercise, the jury should consider that defendants had a competing obligation under the Eighth Amendment to ensure the safety of prisoners, including protecting prisoners from each other. In considering these factors, you should give deference to prison officials in the adoption and execution of policies and practices that in their judgment are needed to preserve discipline and to maintain internal security in a prison.
The district court initially agreed to the language but, after plaintiff objected, declined to include it on the ground that “deference” was “undefined.” Because defendants challenge the resulting jury instruction as an incomplete, and therefore incorrect, statement of the law our review is de novo. Clem v. Lomeli, 566 F.3d 1177, 1180-81 (9th Cir.2009); Dang v. Cross, 422 F.3d 800, 804-06 (9th Cir.2005).
Plaintiff argues that defendants failed to preserve their objection below. See Fed.R.Civ.P. 51(d)(2). But the record shows that defendants contested the district court’s decision not to include the proposed language and made the grounds for their position clear, citing relevant authority. An “objection need not be formal,” and defendants’ proffered language was “sufficiently specific to bring into focus the precise nature of the alleged error.” Inv. Serv. Co. v. Allied Equities Corp., 519 F.2d 508, 510 (9th Cir.1975). Nor did the district judge’s vague statement that defendants “may” have an opportunity to change his mind counter the overall impression that raising the issue again via formal objection would be both “unavailing” and a “pointless formality.” Glover v. BIC Corp., 6 F.3d 1318, 1326 (9th Cir.1993).
It is well established that judges and juries must defer to prison officials’ expert judgments. In Bell v. Wolfish, the Supreme Court explained:
[T]he problems that arise in the day-today operation of a corrections facility are not susceptible of easy solutions. Prison administrators therefore should be accorded wide-ranging deference in the adoption and execution of policies and practices that in their judgment are needed to preserve internal order and discipline and maintain institutional security.
441 U.S. 520, 547, 99 S.Ct. 1861, 60 L.Ed.2d 447 (1979). Six years later, the Court spelled out that deference requires “that neither judge nor jury freely substi*1067tute their judgment for that of officials who have made a considered choice.” Whitley v. Albers, 475 U.S. 312, 322, 106 S.Ct. 1078, 89 L.Ed.2d 251 (1986) (emphasis added). The Court confirmed that Bell remains good law in Farmer v. Brennan, its seminal opinion on challenges to conditions of confinement, which twice cited Bell with approval. 511 U.S. 825, 845, 847, 114 S.Ct. 1970, 128 L.Ed.2d 811 (1994).
The district court declined to give the proposed instruction because the meaning of deference would not be “clear to a lay person.” But “deference” is not Urdu or Klingon; it is a common English word. See, e.g., Michael Crichton, Airframe 78 (1996) (“[S]he certainly knew where all the bodies were buried. Within the company, she was treated with a deference bordering on fear.”). It may be true that deference has varied meanings, Dissent at 454 n. 4, but so do most English words. If the district judge believed the term needed further context or definition, he could have provided it.
Perfect or not, the defendants’ proposed instruction brought the issue of deference to the district court’s attention. “[T]he fact that the proposed instruction was misleading does not alone permit the district judge to summarily refuse to give any instruction on the topic.” Merrick v. Paul Revere Life Ins. Co., 500 F.3d 1007, 1017 (9th Cir.2007). The district court omitted the instruction altogether, rather than modifying it to correct the perceived deficiency. The remaining instructions failed to alert the jury that the deliberate indifference standard “incorporates due regard for prison officials’ ‘unenviable task of keeping dangerous men in safe custody under humane conditions.’ ” Farmer, 511 U.S. at 845, 114 S.Ct. 1970 (quoting Spain v. Procunier, 600 F.2d 189, 193 (9th Cir.1979)). The dissent apparently believes that, because Farmer “incorporates” Bell deference, the use of language drawn from Farmer was adequate to instruct the jury. Dissent at 452. But juries are not clairvoyant and will not know to defer unless they are told to do so.
We have long recognized that additional instruction regarding deference is required in cases applying Whitley to allegedly excessive force by prison officials. See Ninth Circuit Manual of Model Jury Instructions § 9.24 (2007 ed.). The dissent accuses us of improperly extending the Whitley regime to a case involving conditions of confinement. Dissent at 1072-73. But defendants’ proposed instruction was not drawn from Whitley; it was drawn from Bell— itself a conditions of confinement case. Bell, 441 U.S. at 534, 547, 99 S.Ct. 1861. Prison officials are entitled to deference whether a prisoner challenges excessive force or conditions of confinement. See Whitley, 475 U.S. at 322, 106 S.Ct. 1078; Farmer, 511 U.S. at 845, 114 S.Ct. 1970. Indeed, conditions of confinement and use of force are often flip sides of the same coin: A more restrictive confinement may diminish the need for force and vice versa.
As the government recognized at trial, the court’s instruction correctly stated Farmer*s deliberate indifference standard. But the court’s failure to give additional guidance on deference rendered the instruction incomplete and misleading. And the error was also prejudicial. If properly instructed, the jurors might well have reached a different conclusion. Norwood has not met his burden of showing the verdict would “more probably than not” have been the same absent the error. Clem, 566 F.3d at 1182-83. We therefore vacate the jury’s verdict and damages awards.
II
We would normally remand for a new trial, but as defendants are entitled to qualified immunity that is not necessary *1068here. Our dissenting colleague may be right that defendants waived the immunity claim by failing to raise it to the district court during or immediately after trial. On appeal, however, Norwood failed to argue waiver; rather, he addressed qualified immunity on the merits while arguing waiver of the two other principal issues in the case. In Tortu v. Las Vegas Metropolitan Police Department, 556 F.3d 1075 (9th Cir.2009), cited by the dissent, see Dissent at 1075-76, plaintiff explicitly argued that defendants had forfeited qualified immunity by failing to make the proper motion below. Tortu, 556 F.3d at 1081.
It is “well-established” that a party can “ ‘waive waiver’ implicitly by failing to assert it.” Tokatly v. Ashcroft, 371 F.3d 613, 618 (9th Cir.2004); United States v. Garciar-Lopez, 309 F.3d 1121, 1123 (9th Cir.2002); see also Wilson v. Kelkhoff, 86 F.3d 1438, 1445 (7th Cir.1996) (plaintiff waived defendant’s waiver of absolute immunity defense). Norwood waived the defendants’ waiver by addressing the claim on the merits without also making a waiver argument. Cf. Chicano Educ. & Manpower Servs. v. U.S. Dep’t of Labor, 909 F.2d 1320, 1327-28 & n. 5 (9th Cir.1990) (“Yes, we are indeed holding that the Department has waived its right to argue that OEMS waived its right to ask for a waiver... .”). The dissent would have us raise the issue of waiver sua sponte and suggests that we have “discretion” not to reach defendants’ qualified immunity claim. Dissent at 1076-77. But “[t]his court will not address waiver if not raised by the opposing party.” United States v. Doe, 53 F.3d 1081, 1082-83 (9th Cir.1995) (quoting United States v. Schlesinger, 49 F.3d 483, 485 (9th Cir.1995)). Even if we had such discretion, we believe the more prudent course is to resolve the case on the basis of the issues actually briefed and argued by the parties.
When a party waives waiver, we proceed directly to the merits. See, e.g., Tokatly, 371 F.3d at 618-24; Doe, 53 F.3d at 1083-84; Wilson, 86 F.3d at 1445-46. We do not, as the dissent suggests, Dissent at 458-59, engage in plain error review. Defendants are entitled to qualified immunity so long as a right to outdoor exercise in the midst of severe ongoing prison violence was not clearly established at the time defendants acted. See Saucier v. Katz, 533 U.S. 194, 201-02, 121 S.Ct. 2151, 150 L.Ed.2d 272 (2001). “The relevant, dispositive inquiry ... is whether it would be clear to a reasonable officer that his conduct was unlawful in the situation he confronted.” Id. at 202, 121 S.Ct. 2151 (emphasis added).
Three factors weigh heavily in our analysis: First, as Saucier explains, the qualified immunity inquiry is highly context-sensitive, turning on whether it would be clear to a reasonable officer that denying outdoor exercise was unlawful “in the situation he confronted.” Id. The extraordinary violence gripping the prison threatened staff and inmates alike, and there was a serious risk that gangs would press unaffiliated inmates like Norwood into service. See pp. 1065-66 supra. While Norwood argues that a reasonable officer would have known that denying outdoor exercise in the midst of ongoing prison violence violated his rights, he cites just one case — Allen v. Sakai, 48 F.3d 1082 (9th Cir.1995) — for the general proposition that the Ninth Circuit “is one of many[courts] that have held that there is a constitutional right to outdoor exercise for inmates.”
But Allen does not hold that a prisoner’s right to outdoor exercise is absolute and indefeasible, or that it trumps all other considerations. Plaintiffs in Allen survived summary judgment because prison officials there relied on “inconsequential logistical concerns” to justify denying out*1069door exercise. Id. at 1088. Defendants here had substantial reasons for imposing the lockdowns: They were attempting to restore order during a series of brutal attacks, some lethal or nearly so. They did not place “inconsequential logistical concerns” above Norwood’s need for outdoor exercise. And plaintiff offered no evidence that the lockdowns were meant to be punitive or were otherwise implemented in bad faith.
Second, prison officials have a duty to keep inmates safe, and in particular to protect them from each other. Farmer, 511 U.S. at 832-33, 114 S.Ct. 1970; LeMaire v. Maass, 12 F.3d 1444, 1462 (9th Cir.1993). Officials must balance this imperative against other obligations that our laws impose, such as providing outdoor exercise. When violence rises to unusually high levels, prison officials can reasonably believe it is lawful to temporarily restrict outdoor exercise to help bring the violence under control. We’ve explained that “prison officials have a right and a duty to take the necessary steps to reestablish order in a prison when such order is lost. This is for the benefit of the prisoners as much as for the benefit of the prison officials.” Hoptowit v. Ray, 682 F.2d 1237, 1259 (9th Cir.1982). Here, at least one prisoner had died; others (prisoners and guards) had been severely wounded. Defendants had to act decisively to stop the violence.
The dissent claims that the “jury reasonably rejected defendants’ argument that unusual levels of violence justified the long-term deprivations in this case” because “defendants conceded on cross-examination that ‘those types of [violent] incidents occur even when there is no lockdown,’ with the same frequency, and that ‘the violence is pretty steady.’ ” Dissent at 1080 (emphasis omitted). But there’s more to the former warden’s testimony:
While we were on lockdown status, these types of things continued to happen. Either as we incrementally unlocked and released to the small yards for exercise, or sent — you know, releasing — lifting the privileges to go to meals or whatever, violence continued to happen. And if that violence was — occurred based on a decision that we made that we felt it was safe, and we let the small group of prisoners out and something happened, then we would call back our prior decision. [Emphasis added.]
What we understand the warden to be saying is that the lockdowns were effective at curbing violence, and that violence resumed as privileges were restored.
Such decisions are not to be judged with the benefit of hindsight, in any event. It matters not whether the measures taken actually worked but whether prison officials reasonably believed they would be effective in stopping the violence. At most, prison officials here may be faulted for erring on the side of caution by maintaining lockdowns for longer than necessary. But, when it comes to matters of life and death, erring on the side of caution is a virtue. Certainly, no officer could reasonably have anticipated that such prudence would be found to violate the Eighth Amendment.
Third, when balancing the obligation to provide for inmate and staff safety against the duty to accord inmates the rights and privileges to which they are entitled, prison officials are afforded “wide-ranging deference.” Bell, 441 U.S. at 547, 99 S.Ct. 1861. When a “lockdown was in response to a genuine emergency,” and “restrictions were eased as the prison administration determined that the emergency permitted,” we may not lightly second-guess officials’ expert judgments about when exercise and other programs could safely be restored. “These decisions are delicate *1070ones, and those charged with them must be given reasonable leeway.” Hayward v. Procunier, 629 F.2d 599, 603 (9th Cir.1980).
It would be particularly odd to hold that liability attaches in this case, where hindsight validates defendants’ decisions. The record makes clear that a great deal of violence took place during outdoor exercise. While denying outdoor exercise for extended periods carried some risk of harm, officials’ judgment that there was a greater risk of harm from allowing outdoor exercise was certainly reasonable. Indeed, Norwood suffered no injuries from attacks by other inmates or from being denied outdoor exercise — a fact the jury recognized by awarding no compensatory damages. Norwood might have fared less well had prison officials been less cautious. Although exercise is “one of the basic human necessities protected by the Eighth Amendment,” LeMaire, 12 F.3d at 1457, “a temporary denial of outdoor exercise with no medical effects is not a substantial deprivation.” May v. Baldwin, 109 F.3d 557, 565 (9th Cir.1997).
We therefore conclude that a reasonable officer could have believed that restricting Norwood’s outdoor exercise was consistent with the Eighth Amendment. Certainly, no authority clearly established the contrary. Allen didn’t. See pp. 1068-69 supra. And Spain v. Procunier, 600 F.2d 189 (9th Cir.1979), concerned inmates in disciplinary segregation who were denied outdoor exercise as a normal condition of their confinement, id. at 199-200, rather than for safety during emergencies. Not surprisingly, our district courts have found an absence of Eighth Amendment liability on facts similar to these. See, e.g., Jones v. Garcia, 430 F.Supp.2d 1095, 1102-03 (S.D.Cal.2006) (finding no Eighth Amendment violation where prisoner was denied outdoor exercise for ten months — double the longest single period that Norwood’s exercise was restricted — because of ongoing violence); Hayes v. Garcia, 461 F.Supp.2d 1198, 1201, 1207-08 (S.D.Cal.2006) (same for nine-month denial of outdoor exercise); Hurd v. Garcia, 454 F.Supp.2d 1032, 1042-45 (S.D.Cal.2006) (same for five-month denial).
Norwood argues that defendants had no need to conduct lengthy lockdown investigations because those investigations either found that the initial assaults were isolated incidents or else could not determine who else was involved. Norwood also argues that defendants could have limited exercise restrictions to specific groups of prisoners. But the investigations were reasonable precautions, and defendants had no way of knowing beforehand what they would yield. That defendants imposed general lockdowns after some attacks on staff but only group-specific restrictions after some attacks on inmates does not show malicious intent or deliberate indifference. Attacks on staff are, by their nature, more serious challenges to prison authority than attacks on other inmates.
We decline Norwood’s invitation to micro-manage officials whose expertise in prison administration far exceeds our own, and we conclude that defendants are entitled to qualified immunity. On remand, the district court shall enter judgment consistent with this opinion.
Because plaintiff is no longer the prevailing party, we vacate the award of attorney’s fees.
REVERSED.
. Only an Eighth Amendment outdoor exercise claim is before us on this appeal. We therefore express no view as to the race-based aspect of the lockdowns or any potential Equal Protection claim.