Petition granted in part and denied in part, cross-petition granted in part and denied in part, and remanded by published opinion. Judge LUTTIG wrote the opinion, in which Judge WIDENER joined. Judge GOODWIN wrote an opinion concurring in part and dissenting in part.
OPINION
LUTTIG, Circuit Judge.On July 12, 1993, Winson Cox applied for a job as an electrician with Aneco, Inc., a non-union contractor. J.A. 1222. Cox was a paid, full-time union organizer for the International Brotherhood of Electrical Workers, Local Union Number 606 (“the Union”), J.A. 1226, and he sought employment with Aneco to help organize Aneco’s workers. J.A. 779. This process, where union organizers seek to become employees of a company targeted by the union, is known as “salting.” Typically, union “salts” only work for an employer as long as there is a prospect of success at organizing its workers, and they are trained to leave an employer by striking rather than resigning, so as to preserve their rights to reinstatement. J.A. 648^49, 838,1554.
Cox disclosed his motives during his job interview, and Aneco refused to hire him. Id. Five years later, on February 27, 1998, the National Labor Relations Board (“the Board”) held that Aneco’s refusal to hire Cox violated sections 8(a)(1) and (a)(3) of the National Labor Relations Act (“NLRA”). The Board ordered that Cox be made “whole for any loss of earnings and other benefits he may have suffered ... from the date he applied for employment to the date Respondent makes him a valid offer of employment.” Aneco, Inc., 325 NLRB 400, 401, 1998 WL 95462 (1998).
In response to the Board’s ruling, Aneco offered Cox employment on April 1, 1998. J.A. 1219. Cox accepted the offer and worked for Aneco for about five weeks, leaving during an unfair labor practice strike called by a Local from Tampa. J.A. 932. Cox never made an offer to return to work for Aneco nor did he request reinstatement. J.A. 932.
Paid union organizers who seek employment with other companies are protected by the National Labor Relations Act. See NLRB v. Town & Country Electric, Inc., 516 U.S. 85, 116 S.Ct. 450, 133 L.Ed.2d 371 (1995). Aneco conceded that its refusal to hire Cox in 1993 was an unfair labor practice, J.A. 1029, however, Aneco and the General Counsel were unable to agree on the appropriate amount of backpay owed to Cox. The General Counsel sought backpay in the amount of $47,349.29, for ten of the nineteen quarters between July 12, 1993 (the date Aneco unlawfully refused to hire Cox) and April 1, 1998 (the date Aneco hired Cox). J.A. 9 10.1 Aneco opposed this, arguing that Cox did not conduct a reasonable search for interim employment during those ten quarters and, hence, did not fulfill his duty to mitigate his income loss. In the alternative, Aneco contended that the period of *329Cox’s backpay award should be far shorter than the ten quarters sought by the Board because it is wrong to assume that Cox, had he been hired by Aneco in July of 1993, would have continued working at Aneco through April 1, 1998. Aneco argued that Cox, as a union “salt,” would have left Aneco when his employment there no longer serv,ed the Union’s organizational interests; hence, Cox would not have worked ten quarters for Aneco and should not be awarded $47,349.29 in back-pay.
After a compliance hearing, the Administrative Law Judge rejected Aneco’s argument that Cox failed to mitigate his income loss. J.A. 1050-51. However, the ALJ refused to award Cox the full $47,349.29 in backpay sought by the General Counsel, and instead awarded Cox five weeks of back pay in the amount of $1,461.15. J.A. 1052. Noting that Cox, as a union “salt,” “would have spent no more time working for [Aneco] than necessary to organize its employees or conclude that such organizing would not be practical,” J.A. 1040, the ALJ concluded that, had Aneco hired Cox in July of 1993, he would have only worked five weeks for Aneco. J.A. 1051. In so concluding, the ALJ relied on the fact that Cox, when finally hired by Aneco in April of 1998, worked only for five weeks before leaving.
The Board reversed the ALJ’s finding that Cox would have only worked five weeks for Aneco had he been hired in 1993, stating that Aneco failed to present “specific evidence” on this issue. J.A. 1050. Relying on the “well-established principle that ‘[t]he Board resolves compliance-related uncertainties or ambiguities against the wrong-doer,’ ” the Board ordered that Aneco pay Cox the full $47,349.29 in backpay sought by the General Counsel. J.A. 1050 (citations omitted). The Board also found, as did the ALJ, that Cox fulfilled his duty to mitigate. J.A. 1050 n. 3.
Aneco petitions this court for review, and the Board cross-petitions for enforcement of its order. For the reasons that follow, we grant enforcement in part, deny enforcement in part, and remand.
I.
Title 29, U.S.C. § 160(c) authorizes the Board to award backpay in response to an unfair labor practice. However, a backpay order may only serve as a compensatory, make-whole remedy, not a punitive sanction or deterrent. See NLRB v. Pepsi Cola Bottling Co. of Fayetteville, Inc., 258 F.3d 305, 314 (4th Cir.2001). A backpay order is a means to “restore the situation ‘as nearly as possible, to that which would have obtained but for the illegal discrimination.’ ” Coronet Foods, Inc. v. National Labor Relations Board, 158 F.3d 782, 798 (4th Cir.1998) (quoting Phelps Dodge Corp. v. NLRB, 313 U.S. 177, 194, 61 S.Ct. 845, 85 L.Ed. 1271 (1941)).
Aneco raises two challenges to the Board’s award of backpay, and we address each for abuse of discretion. See Coronet Foods, 158 F.3d at 798 (4th Cir.1998).
A.
1.
Aneco first argues that Cox did not conduct a reasonable job search between July 12, 1993 and April 1, 1998 and, therefore, failed to mitigate his income loss. After Aneco refused Cox employment in 1993, Cox did not embark on the type of thorough job search one would expect from one who is unemployed. There were several reasons for this failure, all related to Cox’s role as a union “salt.” First, Cox already had a full-time job with the Union, which dampened his financial incentives to *330obtain additional employment. J.A. 716. Moreover, because Cox’s purpose in seeking a second job was to organize the workers of that company on behalf of the Union, Cox only applied to companies where there was a realistic chance to organize their workers. The Union forbade Cox from applying to work for companies that were already unionized, including all companies that hired through the Union’s hiring hall. J.A. 1042. In addition, Cox could not work for small companies with too few employees to be of organizing interest to the Union, J.A. 579, 1004, nor large companies with so many employees that organizing them would be difficult, J.A. 576, 1036. Given these restrictions, Cox visited a total of only 50 companies during the ten quarters for which the Board awarded backpay. J.A. 1469.
Finally, in addition to the narrow scope of his job search, Cox further hurt his chances of finding employment by bringing other electricians with him when he applied for a job, some of whom were better qualified than he. J.A. 860-61, 1232.2 Apparently, Cox brought his friends along to serve as potential witnesses at an unfair labor practice hearing, and also to increase the number of union organizers working for the non-union company.
Not surprisingly, although he maintained his full-time employment with the Union, Cox never found another job to “salt” until Aneco offered him employment in 1998.
Despite the limited nature of Cox’s job search, the Board held that Cox fulfilled his duty to mitigate his income loss. According to the Board, an employer seeking to prove a failure to mitigate by a union “salt” must show that “the Union’s policies unreasonably limited [the discriminatee’s] job search.” J.A. 1050 n. 3. Rejecting the notion that “the mere existence of any union restrictions was per se unreasonable,” the Board held that Aneco failed to show that any specific restrictions on Cox’s job search imposed by the Union were unreasonable. J.A. 1050 n. 3.
2.
Employees who lose their jobs as a result of an unfair labor practice must mitigate their damages by making a “reasonable effort to obtain interim employment,” and the burden of proving a failure to mitigate rests on the employer. Coronet Foods, 158 F.3d at 800. If Cox had been unemployed, rather than a full-time Union “salt,” during the time of his job search, we would hold without hesitation that he failed to make a “reasonable effort” to obtain interim employment. For *331the typical person seeking work, it cannot be considered a “reasonable effort” to eliminate all large-scale and small-scale employers from one’s job search, and we doubt it can be considered a “reasonable effort” to apply for a job with a group of friends, absent a clear understanding from the potential employer that a bloc of workers is needed.
Cox, however, was not an unemployed person looking for a job; he was a full-time employee of the Union and his purpose in seeking further employment was to advance the Union’s organizational interests. Thus, the crucial issue is whether Cox’s status as a paid union organizer permitted the Board to find that his job search represented a “reasonable effort,” even though such a search could not be deemed reasonable if undertaken by an ordinary, unemployed discriminatee. Given the deference owed to the Board in determining backpay remedies, we conclude that it was permissible for the Board, in determining whether Cox undertook “reasonable efforts” to obtain interim employment, to take into account the duties he owed to his union employer. Previous Board decisions have held that limits on job searches designed to accommodate a discharged worker’s responsibilities to another employer are reasonable, see Acme Bus Corp., 326 NLRB 1447, 1449, 1998 WL 723995 (1998) (holding that discriminatee fulfilled his duty to mitigate even though he limited his search to jobs with starting times after 8:30 am, to accommodate his full-time job as a nursing assistant); American Pacific Concrete Pipe v. General Truck Drivers Union, 290 NLRB 623, 627, 1988 WL 213915 (1988) (holding that discriminatee was not required to accept a job that would require him to abandon active duty service in the Air Force reserve), and we see no reason to question the propriety of those decisions.
We do not hold, however, that the Board may find that any restrictions on an interim job search caused by a discriminatee’s duties to another employer are reasonable per se. Compare Tualatin Electric, Inc., v. NLRB, 253 F.3d 714, 719 (D.C.Cir.2001) (stating that the Board may limit the duty to mitigate “so as not to require a salt to accept employment that would subject him to union discipline or require him to abandon full union membership”). We could not, for example, uphold a finding of mitigation if the limits on a discriminatee’s job search, ostensibly caused by his duties to another employer, were not reasonably related to that employment. In this case, however, we find that the Board could, without abusing its discretion, find that Cox’s limited interim job search was reasonable given his duties as a union salt. While applying for jobs in groups did hurt Cox’s chances of obtaining employment, Aneco is unable to show that such was “unreasonable” given the Union’s need for multiple “salts” on a job site. In addition, while only 50 employers in ten quarters does not seem like a lot to visit, Aneco has failed to show that Cox neglected other employers who were also fertile targets for union organizing.
We conclude that the Board did not abuse its discretion in rejecting Aneco’s argument that Cox failed to mitigate his damages.
B.
Aneco next contests the Board’s decision to award Cox backpay for ten quarters, rather than for five weeks, challenging the Board’s presumption that, had Aneco hired him on July 12, 1993, Cox would have remained on the job through April 1, 1998. Aneco argues that Cox would have quit working for Aneco when it *332no longer served the Union’s interests for Cox to stay, and that this would have occurred long before April 1,1998.
The Board held that Aneco, as a wrongdoing employer, bears the burden of proving that Cox would not have remained at the job which he was unlawfully denied. J.A. 1049. Aneco failed to carry its burden, according to the Board, because Ane-co did not present any “specific evidence” that Cox would not have worked five years for Aneco, and that any uncertainties as to this must be resolved against the wrongdoer, Aneco. J.A. 1050.
Given the evidence presented in this case, we conclude that the Board abused its discretion in calculating the backpay period on the assumption that, had he been hired in 1993, Cox would have worked for Aneco for five years. Aneco did present specific evidence to show that this assumption was indefensible. First, Cox was not an ordinary employee, but a union “salt” whose sole purpose in seeking employment with Aneco was to organize its workers. Accordingly, it was undisputed that Cox would have left his job at Aneco when it no longer served the Union’s organizational interests. J.A. 572. While Cox’s duties to the Union allowed us to uphold the Board’s finding that Cox mitigated his damages by conducting a reasonable job search, his duties to the union undermine the Board’s assumption that Cox would have stayed on the job for five years.
Second, Cox actually worked for Aneco in 1998 after the Board ordered him reinstated, and he worked for only five weeks before leaving during an unfair labor practice strike. J.A. 837. Although the Board correctly noted that this does not prove that Cox would have “invariably” departed from Aneco in five weeks had he been hired in 1993, J.A. 1050, it is still strong evidence that Cox’s stint at Aneco would have been far less than five years, and strongly suggests the Board’s award of backpay serves a punitive rather than compensatory function.
Finally, there are no examples in the record of a union “salt” ever remaining on the payroll of another company for five years. Harry Brown, the Union’s business manager, testified that some organizing campaigns against companies other than Aneco lasted several years, J.A. 641-44, and also testified that the Union might have desired to keep Cox on Aneco’s payroll for five years “if it was productive,” J.A. 571-72. But there is no testimony that a union “salt” was employed at a single company for a five-year period as part of these campaigns, nor is there any indication that Cox would have stayed at Aneco for five years given the circumstances at Aneco in 1993.3
*333We acknowledge, as did the ALJ, that any calculation of how long Cox would have worked if Aneco had hired him on July 12, 1993 is “somewhat speculative.” However, a backpay order must “restore the situation ‘as nearly as possible, to that which would have obtained but for the illegal discrimination.’ ” Coronet Foods, Inc., 158 F.3d at 798. In light of Cox’s role as a union salt, as well as the fact that Cox only worked five weeks for Aneco when hired in 1998, we cannot enforce the Board’s award of backpay premised on the assumption that Cox would have worked five years for Aneco had he been hired in July of 1993. To do so in the face of this evidence would provide a windfall to Cox and would exceed the Board’s authority to award only make-whole remedies, and not punitive sanctions. See Pepsi Cola Bottling Co., 258 F.3d at 314. Unlike NLRB v. Ferguson, 242 F.3d 426, 430 (2d Cir.2001), where there was an “absence of record evidence” as to how long the unlawfully discharged union “salt” would have remained with the employer, there is ample evidence in the record to suggest that Cox would not have worked five years for Aneco. The Board’s contrary holding in the face of this evidence is an abuse of discretion, and cannot be enforced.
On remand, based upon the record in the case, we would expect the appropriate, make-whole remedy for Cox to be somewhere around the five weeks of backpay awarded by the ALJ. However, there may be circumstances, unforeseen to us, that would justify an award slightly beyond that amount. The Board’s responsibility on remand is to fashion a compensatory remedy that will restore Cox, as nearly as possible, to the circumstances that he would have enjoyed but for Aneco’s illegal discrimination.
CONCLUSION
We enforce the Board’s finding that Cox mitigated his income loss, but decline to enforce the Board’s $47,349.29 award of backpay. The ease is remanded to the Board to fashion a remedy that will restore Cox, as nearly as possible, to the circumstances that he would have enjoyed but for Aneco’s illegal discrimination.
It is so ordered.
. For nine of the quarters during that five-year period, the General Counsel conceded there was no backpay liability owed to Cox.
. The record contains a letter dated July 17, 1996, from Val Chu to Cox, which states, in part:
Dear Mr. Cox:
The purpose of this letter is to let you know that we have filled our needs for journeymen electricians and that we will not be offering you a position with our company. We have filled the immediate needs by hiring Mr. Albert Weber. As you know, Mr. Weber applied at the same time as you did, and highlighted his union membership. Prior to hiring Mr. Weber, we offered a position to Mr. Gary Johnson. Mr. Johnson declined to accept our job offer, telling me that he had secured other employment. As you know, Mr. Johnson also was with you when you most recently applied, and his application includes a notation that he is a "volunteer unión organizer." ...
Beyond the fact that there are sufficient candidates available to us, I do want you to know that we consider that your lack of active working at the electrical trade for the last 14 (fourteen) years as indicated on your application, makes you a candidate of last resort.... We believe that hiring people with recent experience is a more sound business practice in light of their current acclimation to the daily requirements of the craft, including safety habits.
. The dissent contends that Aneco did not meet its evidentiary burden to rebut, by a preponderance of the evidence, the Board's presumption that Cox would not have worked five years for Aneco had he been hired in 1993. However, we believe that the dissent's reasoning, as well as the Board's, places too high a burden of proof on Aneco.
Aneco is not required to prove to a certainty, or beyond a reasonable doubt, that Cox would have left Aneco's employ before April 1, 1998. Moreover, Aneco need not pinpoint a precise date or time when Cox would have quit working. Aneco must only show that it is more likely than not that Cox would not have worked for Aneco during the entire five-year backpay period.
This case is unlike Ferguson, where there was an absence of evidence regarding how long the union salt, whom the employer unlawfully refused to hire, would have stayed on the job. Also, the disputed backpay period in Ferguson was "only” ten months, not five years.
We believe the evidence of Cox’s role as a union salt, the fact that he only worked five weeks for Aneco in 1993, and the lack of any evidence of a union salt ever working for an *333employer for the extraordinarily long period of five years, was more than adequate to rebut, by a preponderance of the evidence, the Board’s presumption, and that the Board abused its discretion in holding otherwise.