Defendant Robert V. Timm appeals from the trial court’s denial of his motion to dismiss plaintiff’s complaint for money damages. Defendant also challenges the measure used by the trial court in fixing plaintiff’s damages. We hold that the trial court did not err in refusing to dismiss plaintiff’s complaint and that defendant waived his right to challenge the trial court’s award of damages by failing to plead or argue mitigation of damages as an affirmative defense.
This action arose out of an automobile accident that occurred on December 2, 1979. Plaintiff was sitting in his car at an intersection, waiting for the traffic signal to change, when defendant drove into the rear of plaintiff’s vehicle. Plaintiff sued for damages to his car.
In a bench trial, plaintiff presented undisputed evidence that he had recently paid $6,500 for the car and that the estimated cost of repairs was $8,362.57. Plaintiff also argued that he was entitled to recover storage charges at the rate of $5 per day from the date of the accident through the date of trial, plus $150 as the cost of obtaining alternative transportation pending repair of his vehicle. Defendant objected to the admission of evidence relating to storage costs “as not being material” because they had not been specifically alleged as damages in plaintiff’s complaint. The court overruled that objection. After plaintiff rested, defendant moved to dismiss the complaint “on the basis that it hasn’t stated a cause of action.” After hearing defendant’s argument that the complaint was defective because it did not allege the specific elements of negligence — duty, breach, and causation — the judge allowed amendment of the complaint to conform with the proof of negligence presented at trial. Defendant’s motion to dismiss was denied.
*1353After considering the evidence, the court awarded damages of $6,650, which was calculated as the purchase price of plaintiffs vehicle ($6,500), plus plaintiffs cost for obtaining alternative transportation ($150). The court specifically adopted the cost of plaintiffs vehicle as the measure of damages rather than the sum of repair costs plus storage costs, which totaled more than $9,000.
Defendant now appeals on the ground that the trial court improperly denied his motion to dismiss. Defendant also argues that the trial court improperly considered plaintiffs claim for storage charges in calculating damages because plaintiff had not attempted to mitigate those costs. Defendant’s first point lacks merit. Utah Rule of Civil Procedure 8(a) requires simply that “a pleading which sets forth a claim for relief ... shall contain (1) a short and plain statement of the claim showing that the pleader is entitled to relief; and (2) a demand for judgment for the relief to which he deems himself entitled.” The pleadings must be sufficient to give “fair notice of the nature and basis of the claim asserted and a general indication of the type of litigation involved.” Blackham v. Snelgrove, 3 Utah 2d 157, 161, 280 P.2d 453, 455 (1955). Rule 8(a) is to be liberally construed when determining the sufficiency of a plaintiffs complaint. See Cheney v. Rucker, 14 Utah 2d 205, 211, 381 P.2d 86, 91 (1963); Williams v. State Farm Insurance Co., Utah, 656 P.2d 966, 970-71 (1982).
Plaintiffs complaint, although meager, sufficed to inform defendant of the plain nature and basis of the claim against him. Although negligence and its technical elements were not pleaded specifically, the whole case, including the evidence and arguments of counsel, proceeded on the basis of negligence. Defendant was neither surprised at trial nor unable to present legitimate defenses which he may have had. See, e.g., Rosenlof v. Sullivan, Utah, 676 P.2d 372 (1983).
If there is any question about the sufficiency of the complaint, it was removed when the trial court, acting under Rule 15(b), allowed amendment of the pleadings to conform with the evidence adduced at trial. This procedure is much preferred to the alternative of dismissal, especially where a trial has proceeded to conclusion on the existing pleadings and where the defendant has suffered no prejudice by reason of any deficiency in the pleadings. As this Court said in Mabey v. Kay Peterson Construction Co., Utah, 682 P.2d 287, 289 (1984),
[W]hen issues not raised by the pleadings are tried by express or implied consent they shall be treated in all respects as if they had been raised in the pleadings. Rule 15(b) [Utah R.Civ.P.]; Poulsen v. Poulsen, Utah, 672 P.2d 97 (1983); General Insurance Co. of America v. Carnicero Dynasty Corp., Utah, 545 P.2d 502 (1976); Holdaway v. Hall, 29 Utah 2d 77, 505 P.2d 295 (1973).
Defendant’s second argument on appeal is that plaintiff failed to mitigate his damages. Apparently, plaintiff allowed the damaged vehicle to remain at the repair shop for almost four years pending the outcome of this suit, resulting in storage charges in excess of $3,000. The trial court reasoned that because the actual or special damages resulting from the accident, cost of repair, cost of alternative transportation, and including storage costs, exceeded the purchase price of the vehicle, the proper calculations of a judgment should be only the price of the newly purchased vehicle in order to avoid giving plaintiff a windfall. Defendant suggests that the proper measure of damages should be limited to $3,362.57 for the cost of repairs, plus $150 as the cost to plaintiff of arranging alternative transportation. We assume this argument would have merit if properly raised, but it has reared its head for the first time on appeal. “Mitigation of damages is an affirmative defense.” Pratt v. Board of Education, Utah, 564 P.2d 294, 298 (1977), aff'd on rehearing, 569 P.2d 1112 (1977). Affirmative defenses must be set forth in responsive pleadings, Utah R.Civ.P. 8(c), and are usually waived if not *1354so pleaded. Utah R.Civ.P. 12(h). This Court has explained the reason for this result:
Since an affirmative defense raises matters outside the scope of plaintiffs prima facie case, any matter which does not tend to controvert the opposing party’s prima facie case should be pleaded and is not put in issue by denial pursuant to Rule 8(b) [Utah R.Civ.P.].
Pratt v. Board of Education, 564 P.2d at 298.
Defendant did not raise mitigation of damages as an affirmative defense in his answer to the complaint. Nor did he present evidence or argument on mitigation at trial. If he had, he might have been entitled to post-trial amendment of his answer under Rule 15(b) to include mitigation of damages as an affirmative defense. Price Orem Investment Co. v. Rollins, Brown and Gunnell, Inc., Utah, 713 P.2d 55, 58-59 (1986): see also Cheney v. Rucker, 14 Utah 2d at 211, 381 P.2d at 91; Loader v. Scott Construction Corp., Utah, 681 P.2d 1227, 1228-29 (1984).
Toward the end of trial, the court' discussed damages generally and mentioned the concept of mitigation and observed that neither party had addressed it. Defendant’s counsel did not pick up on the issue then or at any other time during the proceeding. A party objecting to the trial court’s ruling must make a clear and succinct objection to the court at the time the error first becomes apparent. The court must be afforded a timely opportunity to correct its error, or the objecting party will have waived its right to argue the objection on appeal. Beehive Medical Electronics, Inc. v. Square D Co., Utah, 669 P.2d 859, 861 (1983). This is so whether the error runs to jury instructions, as to which objections are governed by Rule 51, see, e.g., Morgan v. Quailbrook Condominium Co., Utah, 704 P.2d 573, 579 (1985), or whether the error involves a question of law or procedure in a bench trial. See, e.g., Callan v. Biermann, 194 Kan. 219, 398 P.2d 355, 357 (1965). Since the matter was not raised below, we will not consider it.
For the foregoing reasons, we affirm. Costs to plaintiff.
HALL, C.J., and DURHAM, J., concur.