This сase arises from a series of loans made by Firestone Financial Corporation (“Firestone”) to JHM Equipment Leasing Company (“JHM”). After JHM defaulted on the loans, Firestone filed suit against JHM, John R. Meyer (JHM’s owner), and
I
BACKGROUND
Firestone is a finance company incorporated under the laws of Massachusetts with its principal place of business in that state. JHM is an Illinois corporation that rents commercial laundry machines to apartment building owners in Chicago and its suburbs. Mr. Meyer owns and operates JHM and two related companies, J H Meyer Enterprises, Inc. (“Meyer Enterprises”) and Dolphin Laundry Services, Inc. (“Dolphin”). Mr. Meyer is an Illinois citizen, residing in Hinsdale, Illinois; his three' companies are all incorpоrated in Illinois and have their principal place of business in that state.
Between June 2012 and June 2013, Firestone made four separate loans to JHM, totaling $254,114.99. Each loan was secured by JHM’s laundry equipment and guaranteed by Meyer Enterprises, Dolphin, and Mr. Meyer.
Between June and August of 2013, JHM defaulted on each of its four loans. Shortly afterward, Firestone filed this diversity action in the district court against Mr. Meyer and his three companies, alleging claims for breach of contract, breach of guaranty, replevin, and detinue.
The defendants filed an answer, denying the allegations of breach and asserting a counterclaim of promissory estoppel. In this counterclaim, the dеfendants alleged that in November 2012, after Firestone’s first two loans to JHM, Firestone vice president Dan McAllister had represented that his company “wanted to expand [its] investment in the laundry business,” and that it “would create a $500,000 line of credit” to fund the defendants’ equipment purchases in 2013.
The dеfendants’ answer also raised four affirmative' defenses, including that of promissory estoppel and prior breach of contract. These latter two defenses were based on the same factual allegations as the defendants’ counterclaim.
In February 2014, Firestone moved to dismiss the defendants’ counterclaim under Rule 12(b)(6). The сompany submitted that the claim was implausible because it was premised on “the unheard of position that Firestone, a corporation with nearly 50 years in business, [would make] a handshake deal to loan half a million dollars to a start up business to be secured after the fact.”
The district court held a status hearing on the remaining claims in April 2014. The court started the hearing by discussing the defendants’ efforts to obtain substitute counsel. Mr. Meyer informed the court that he was working to obtain counsel and that his corporate codefendants would have representation within approximately one week. In response, Firestone asserted that the defendants were taking too long to obtain counsel and that the court should rule on its pending motion to dismiss. Having apparently forgotten about this motion, the court replied, “Well, wait just a minute. Let me get the chambers file. You are right, I have given Mr. Meyer a lot of leeway.”
Shortly afterward, Firestone moved for summary judgment on its remaining breach of guaranty claim against Mr. Meyer. Regarding Mr. Meyer’s promissory estoppel and рrior-breach-of-contract defenses, Firestone asserted that, because those defenses were based on the same factual allegations as Mr. Meyer’s counterclaim, they were barred by the court’s earlier ruling dismissing his counterclaim as implausible. The court later granted Firestone’s motion for summary judgment. In doing so, it did not specifically discuss either of the above-referenced affirmative defenses.
Mr. Meyer timely appealed.
II
DISCUSSION
Mr. Meyer now challenges both the district court’s dismissal of his counterclaim as well as the court’s order awarding summary judgment to Firestone. We address these issues in turn.
A.
Mr. Meyer first submits that the district court erred in dismissing his counterclaim under Rule 12(b)(6). “A motion to dismiss pursuant to [Rule] 12(b)(6) challenges thе viability of a complaint by arguing that it fails to state a claim upon which relief may be granted.” Camasta v. Jos. A. Bank Clothiers, Inc.,
1.
As a threshold matter, Firestone contends that Mr. Meyer waived his right to appeal this issue by failing to respond to its motion to dismiss in the district court. We cannot accept this view. Although a party generally forfeits an argument or issue not raised in response to a motion to dismiss, “it is well settled that [this] rule does not prevent a party from attacking on appeal the legal theory upon which the district court based its decision.” Sidney
Here, Mr. Meyer does not challenge the district court’s decision based on a newly raised argument or on an issue not considered by the district court; rather, he merely submits that the court’s reason for dismissing his counter-claim — because its factual allegations were implausible — was wrong. No principle of waiver precludes Mr. Meyer from raising this limited argument on appeal. See Sidney Hillman Health Ctr. of Rochester,
2.
We now turn to the merits of Mr. Meyer’s appeal. To survive a motion to dismiss under Rule 12(b)(6), “a complaint must allege ‘sufficient factual matter to state a claim to relief that is plausible on its face.’ ” Gogos v. AMS Mech. Sys., Inc.,
Here, Mr. Meyer’s countеrclaim alleged (1) that Firestone vice president Dan McAllister had represented that Firestone “wanted to expand [its] investment in the laundry business,” and that it “would create a $500,000 line of credit” to fund the defendants’ equipment purchases in 2013, and (2) that after “establishment of the line of credit was delayed, McAllister represented to JHM that if JHM purchased the equipment necessary to expand its business, Firestone would finance equipment packages in 2013 on the same terms and conditions as the First and Second Loans.”
The district court, however, did not treat these well pleaded factual allegations as true. Rather, the court determined that it was “implausible to allege that somehow Firestone committed orally to provide a half million dollars unsecured to what was essentially a comparative startup business.”
Once Mr. Meyer’s well-pleaded factual allegations are accepted as true, we have no difficulty concluding that they are sufficient to state a plausible claim of promissory estopрel. “To establish [such] a claim, the plaintiff must prove that (1) defendant made an unambiguous promise to plaintiff, (2) plaintiff relied on such promise, (3) plaintiffs reliance was expected and foreseeable by defendants, and (4) plaintiff relied on the promise to its detriment.” Newton Tractor Sales, Inc. v. Kubota Tractor Corp.,
Here, Mr. Meyer alleges that Firestone, through McAllister, told him
B.
Mr. Meyer also challenges the district court’s award of summary judgment to Firestone. Specifically, he submits that the “court erred in disregarding [two of his] affirmаtive defenses because they were based on the same facts as [his] counterclaim, which the district court concluded was implausible.”
As we noted earlier, Mr. Meyer raised several affirmative defenses in his answer, two of which — a promissory estoppel defense and prior-breach-of-contract defense — were based on the same factual allegations as his counterclaim. In moving for summary judgment, Firestone submitted that these two defenses were barred by the district court’s earlier ruling dismissing Mr. Meyer’s counterclaim as implausible. Firestone offered no other ground for rejecting these defenses.
In awarding summary judgment, the district court did not specifically discuss either of these defenses. Rather, at the hearing on Firestone’s motion, the court simply stated that none of the arguments “advanced by Mr. Meyer really undercut the entitlement of Firestone to summary judgment” and that the court did not “see any need ... to expend time and effort for purposes оf knocking out the arguments advanced by Mr. Meyer.”
These conclusory remarks do not explain clearly why the district court thought that Mr. Meyer’s promissory estoppel and prior-breach-of-contract defenses were insufficient to preclude summary judgment. Although both parties appear to agree that the court rejected these defenses for the same reason that it dismissed Mr. Meyer’s counterclaim (i.e., becаuse they were premised on implausible factual allegations), nowhere does the court expressly adopt this rationale.
Ordinarily, when faced with an ambiguity such as this, we would remand the case to the district court for clarification of its reasoning pursuant to Circuit Rule 50.
Conclusion
For the foregoing reasons, the judgment of the district court is reversed, and the case is remanded to the district court for proceedings consistent with this opinion.
REVERSED AND REMANDED
Notes
. R.23 at 23.
. Id. at 25.
. R.42 at 5.
. R.106 at 3.
. The district court had jurisdiction over this case under 28 U.S.C. § 1332. Our jurisdiction is premised on 28 U.S.C. § 1291.
. See also Allison v. Ticor Title Ins. Co.,
Firestone submits that our decisions in Alioto v. Town of Lisbon,
. See also Ashcroft v. Iqbal,
. R.23 at 23, 26.
. R. 106 at 4.
. Appellant's Br. 15.
. R.108 at 2-3.
. R.90 at 1.
. Circuit Rule 50 reads, in relevant part, as follows:
Whenever a district court resolves any claim or counterclaim on the merits, terminates the litigation in its court (as by re*829 manding or transferring the case, or denying leave to proceed in forma pauperis with or without prejudice), or enters an interlocutory order that may be appealed to the court of appeals, the judge shall give his or her reasons, either orally on the record or by written statement.
