Defendant SunTrust Bank (“SunTrust”) appeals the district court’s order denying its motion to compel plaintiff Sara Krinsk to submit her claims to arbitration pursuant to an arbitration agreement governed by the Federal Arbitration Act (“FAA”), 9 U.S.C. § 1 et seq. The district court held that SunTrust had, by participating in the litigation for nine months prior to requesting that the case be submitted to arbitration, waived its contractual right to compel arbitration. In its appeal, SunTrust argues that Krinsk’s submission of an amended complaint revived its right to compel arbitration, notwithstanding its previous waiver of that right. We find merit in SunTrust’s argument and therefore vacate the order and remand to the district court for further proceedings.
I.
A.
In December 2006, Krinsk applied for and obtained from SunTrust a home-equity loan that allowed her to draw from a $500,000 home-equity line of credit (“HE-LOC”) collateralized by Krinsk’s $1.6 million Sarasota, Florida home. In securing the loan, Krinsk executed SunTrust’s standard-form loan agreement, known as an *1197 “Access 3 Equity Line Account Agreement and Disclosure Statement” (the “Loan Agreement”). Among the Loan Agreement’s terms is an arbitration clause requiring Krinsk and SunTrust to resolve all disputes through binding arbitration whenever either party elects arbitration and provides the other party with written notice of the election to arbitrate. Such notice of election “may be given after a lawsuit has been filed and/or in papers filed in the lawsuit.” If a party elects to submit the dispute to arbitration, the Loan Agreement precludes resolution of the claims by class action. 1
B.
In October 2008, SunTrust unilaterally suspended Krinsk’s right to access $400,000 of her HELOC. SunTrust earlier had mailed Krinsk a letter requesting that she provide SunTrust with updated financial information; SunTrust contends that its decision to suspend Krinsk’s HE-LOC was based on the information she subsequently provided in response to that request. Indeed, SunTrust informed Krinsk by letter that it was suspending her HELOC access due to “reasonable concern that [she would] be unable to fulfill [her] financial payment obligations with [SunTrust] under [her] credit line account because of a material change in [her] financial circumstances.” 2
Krinsk alleges that SunTrust’s justification for suspending her account was pretextual. She claims that SunTrust suspended her HELOC, as well as those of other Florida homeowners who had obtained HELOCs from SunTrust around the same time, as part of a scheme Sun-Trust concocted to restore its capital reserves, which had become depleted in the Fall of 2008. According to Krinsk, HELOCs like hers — those sold to Florida residents between the late 1990s and early 2008 and secured by Florida real property — were among the highest-rated risk elements in SunTrust’s debt portfolio, and SunTrust, recognizing that it had a significant concentration of credit risk arising from these loans, aimed to systematically liquidate the loans’ available credit balances. To do that, SunTrust mailed letters, like Krinsk received, requesting that HELOC customers provide SunTrust with updated financial information. This, Krinsk posits, provided SunTrust with a means to assert contrived justifications for suspending customers’ access to their HELOCs — i.e., under the guise of conducting reviews of customers’ financial positions. The most vulnerable targets of SunTrust’s scheme, adds Krinsk, who is 92-years-old, were elderly HELOC borrowers, from whom SunTrust anticipated little resistance.
C.
Based on the foregoing allegations, Krinsk, on May 15, 2009, filed a class-action complaint (the “Original Com *1198 plaint”) against SunTrust — as well as Sun-Trust’s corporate parent, SunTrust Banks, Inc. (“SBI”), 3 and SunTrust and SBI’s President and Chief Executive Officer James M. Wells III. The Original Complaint stated claims for: (1) financial elder abuse under Florida’s Adult Protective Services Act, § 415.101; (2) breach of contract; (3) deceit; (4) negligent misrepresentation; (5) breach of fiduciary duty; 4 (6) violation of Regulation Z of the Truth in Lending Act (“TILA”), 12 C.F.R. § 226.5b(f); and (7) breach of the implied covenant of good faith and fair dealing. It also requested declaratory relief concerning Krinsk’s right to access her HELOC.
The Original Complaint defined the proposed class as:
all Florida permanent or part-time residents that entered into an agreement with SunTrust entitled “Access 3 Equity Line Account Agreement and Disclosure” and who, after attaining the age of sixty-five (65), received a letter from SunTrust between July 1, 2008 and October 16, 2008, requesting updated financial information ... and who were subsequently informed their collateralized credit line had been suspended or reduced during the draw period for purportedly failing to provide the information requested by SunTrust.
Krinsk reasonably estimated, in a later motion for class certification, 5 that this class would “consist[ ] of hundreds of members located throughout Florida.” PL’s Mot. for Class Certification and Mem. of Law in Supp. 7-8, Aug. 13, 2009 (emphasis added).
On July 6, 2009, SunTrust responded to the Original Complaint by filing, in lieu of an answer, a motion to dismiss, challenging the sufficiency of each of Krinsk’s causes of action; SBI and Wells filed a joint motion to dismiss the following day. SunTrust’s motion made no mention of the Loan Agreement’s arbitration clause.
The district court did not rule on the motions to dismiss for over six months, and, in the meantime, the litigation proceeded. On August 10, 2009, for instance, SunTrust and Krinsk jointly filed a Case Management Report in which (1) SunTrust expressly stated that it opposed arbitrating the claims asserted against it in the Original Complaint; (2) SunTrust laid out its discovery plan; 6 and (3) the parties agreed on a proposed discovery deadline, a proposed dispositive motion deadline, on a final pretrial conference date “on or after April 11, 2011 and for trial on or after May 16, 2011.” Moreover, following Krinsk’s August 13, 2009 motion to certify the class defined in the Original Complaint, Sun-Trust levied a vigorous defense against and opposition to class certification and class discovery. 7 Throughout this time, SunTrust did not assert its right to compel arbitration under the Loan Agreement or otherwise indicate its intent to do so.
The district court finally ruled on the motions to dismiss on January 8, 2010, *1199 granting SunTrust’s motion in part 8 and dismissing all of Krinsk’s claims against SBI and Wells. The court also gave Krinsk twenty days’ leave to amend the Original Complaint in light of its order. Subsequently, on January 28, Krinsk filed an amended complaint (the “Amended Complaint”), which asserted revised, but mostly similar, claims against SunTrust only — for (1) breach of contract; (2) violation of Regulation Z of TILA; and (3) breach of the implied covenant of good faith and fair dealing. 9
Because the district court had yet to rule on Krinsk’s motion for class certification, the Amended Complaint also offered a new definition for the proposed class, now defining the class as:
All Florida residents who entered into one or more agreements for a ... [HE-LOC] with SunTrust Bank pursuant to its “Access 3 Equity Line Account Agreement and Disclosure” that was collateralized by real estate located in Florida, and who had the available balance of their HELOC suspended or reduced anytime between January 1, 2007 to the date of class certification (the “Class Period”).
This new definition — now encompassing Florida residents of any age whose HELOCs SunTrust had suspended for any reason during a three-year class period— greatly enlarged the potential size of the putative class. Indeed, Krinsk later estimated, in an amended motion for class certification filed on March 11, 2010, the number of class members to be in the thousands — if not the tens of thousands. See PL’s Am. Mot. for Class Certification and Mem. of Law in Supp. at 7-8, Mar. 11, 2010 (estimating numerosity of amended class definition based on “SunTrust’s own records” which “show that at least 56,758 Access 3 HELOCs issued to residents of Florida and secured by real property located in Florida were suspended or reduced by SunTrust during the Class Period”).
SunTrust promptly answered the Amended Complaint on February 10, 2010. In its answer, SunTrust raised its right to arbitration for the first time since the litigation began, asserting, as an affirmative defense, that the Loan Agreement’s arbitration clause barred Krinsk from pursuing her action in court and demanding arbitration of her claims. SunTrust also filed, along with its answer, (1) a motion, under the FAA, 10 to compel arbitration, 9 U.S.C. § 4, 11 and to stay the action pending arbitration, id. § 3, 12 and (2) a motion to prohibit maintenance of a class action pursuant to the terms of the Loan Agree *1200 ment. Krinsk opposed those motions, claiming that SunTrust had waived its contractual right to compel arbitration. 13
D.
The district court, in an order issued March 26, 2010, denied SunTrust’s motion to compel arbitration, agreeing with Krinsk that SunTrust had waived its right to require arbitration of the claims she asserted in the Amended Complaint. 14
Although arbitration agreements governed by the FAA are to be liberally enforced,
see Moses H. Cone Mem’l Hosp. v. Mercury Constr. Corp.,
Here, the district court found both prongs of the waiver test satisfied in denying SunTrust’s motion to compel arbitration. First, the court determined that SunTrust had acted inconsistently with its right to arbitrate Krinsk’s claims through
*1201
its participation in the litigation up until the filing of its answer and motion to compel arbitration. “[A] party that substantially invokes the litigation machinery prior to demanding arbitration may waive its right to arbitrate,”
S & H Contractors,
Additionally, the district court decided that, due to SunTrust’s actions, Krinsk would suffer prejudice were Sun-Trust permitted to assert its arbitration rights in such an untimely manner. In determining whether the party opposing arbitration has been prejudiced, courts “consider the length of delay in demanding arbitration and the expense incurred by that party from participating in the litigation process.”
S & H Contractors,
SunTrust now appeals the order denying its motion to compel arbitration and to stay the action. Although the order is an interlocutory ruling, SunTrust may appeal it under 9 U.S.C. § 16(a)(1)(A), (B). 19
*1202 II.
In its brief on appeal, SunTrust argues that the district court erred in concluding that the Amended Complaint was immaterial to whether SunTrust had waived its right to compel arbitration. 20 Specifically, SunTrust contends that, even if its invocation of the judicial process operated to waive its right to arbitrate the claims in the Original Complaint, the Amended Complaint “rejuvenated” or revived its right to compel arbitration. Whether Sun-Trust’s position is correct presents an issue of first impression for this court. The decisions of other federal courts that have considered the issue are informative and persuasive. They have held that, in limited circumstances, fairness dictates that a waiver of arbitration be nullified by the filing of an amended complaint. We conclude that this case presents one of those limited circumstances, and that SunTrust’s right to compel arbitration is therefore revived.
Although, under the Federal Rules of Civil Procedure, “an amended complaint supersedes the initial complaint and becomes the operative pleading in the case,”
Lowery v. Ala. Power Co.,
Likewise, a defendant’s waiver of the right to compel arbitration is not automatically nullified by the plaintiffs filing of an amended complaint.
See, e.g., Gilmore v. Shearson/Am. Express Inc.,
The invocation of the judicial process ordinarily establishes a waiver of the defendant’s right to compel arbitration— i.e., such conduct shows, in the normal case, that the defendant intends to elect a judicial forum rather than an arbitral tribunal.
See Cabinetree of Wis., Inc. v. Kraftmaid Cabinetry, Inc.,
In contrast, however, the defendant’s prior waiver should not be nullified, and there should be no revival of the arbitration right, when the plaintiff has filed an amended complaint that does not unexpectedly expand the litigation’s scope. For example, courts have refused to revive the right to compel arbitration where the amended complaint has made only minor factual changes.
See, e.g., Gilmore,
Here, the Amended Complaint is clearly not like the amended complaints in these latter cases. Although, as the district court concluded, the Amended Complaint does merely assert new claims based on the same operative facts as the claims in the Original Complaint, the Amended Complaint is by no means “immaterial.” That conclusion flatly ignored the significance of the new class definition in the Amended Complaint, which greatly broadened the potential scope of this litigation by opening the door to thousands—if not tens of thousands—of new class plaintiffs not contemplated in the original class definition by discarding the old definition’s limits on the class plaintiffs’ age and on the bases for their HELOC suspensions, 21 and by expanding the class period from over three months to over three years.
*1204 This vast augmentation of the putative class so altered the shape of litigation that, despite its prior invocations of the judicial process, SunTrust should have been allowed to rescind its waiver of its right to arbitration. SunTrust’s acts in furtherance of the litigation all occurred prior to the filing of the Amended Complaint and thus concerned the class contemplated in the Original Complaint; SunTrust proceeded in court on the expectation that, if the class action were certified, it would defend itself against only the relatively small plaintiff class defined in the Original Complaint. SunTrust could not have foreseen that Krinsk would expand the putative class in such a broad way nine months into the litigation. Given this unforeseen alteration in the shape of the case, Sun-Trust, in plain fairness, should have been allowed to rescind its earlier waiver through its prompt motion to compel arbitration. 22
In sum, having found that SunTrust’s right to compel arbitration, even if waived with respect to the claims in the Original Complaint, was revived by Krinsk’s filing of the Amended Complaint, we VACATE the district court’s order denying Sun-Trust’s motion to compel arbitration and stay the proceedings and REMAND for further proceedings consistent herewith. 23
SO ORDERED.
Notes
. The Loan Agreement provides in pertinent part:
5. NO CLASS ACTIONS, ETC. ... if you or we elect to arbitrate a claim, neither you nor we will have the right: (a) to participate in a class action in court or in arbitration, either as a class representative, class member or class opponent; or (b) to join or consolidate Claims with claims of any person other than you. No arbitrator shall have authority to conduct any arbitration in violation of this provision.
. SunTrust's letter claimed that the suspension decision was based on a report issued by Equifax, a credit reporting agency, and added that Krinsk could obtain a copy of her credit report directly from Equifax. The letter also informed Krinsk that she could request reinstatement of her borrowing privileges if she were to provide additional financial documentation requested.
. SunTrust is a wholly owned subsidiary of SunTrust Bank Holding Company, which is a wholly owned subsidiary of SBI.
. The claim for breach of fiduciary duty was asserted against SunTrust only.
. Krinsk's motion for class certification, under Fed.R.Civ.P. 23(c)(1), was filed on August 13, 2009.
. The discovery plan covered interrogatories, requests for admissions, production requests, expert witness disclosures, depositions, and the handling of confidential information.
.For example, on September 9, 2009, Sun-Trust filed an opposition to Krinsk’s August 13, 2009 motion for class certification, and, from November to December 2009, SunTrust filed four separate motions for protective orders related to Krinsk’s requests for class-wide discovery.
. The court preserved Krinsk's claims against SunTrust for breach of contract and breach of implied covenant of good faith and fair dealing, and her request for declaratory relief. All other claims against SunTrust were dismissed without prejudice.
. Krinsk also again sought declaratory relief concerning her right to access her HELOC funds.
. There is no dispute that the Loan Agreement "evidenc[es] a transaction involving commerce” and is therefore within the scope of the FAA, 9 U.S.C. § 2.
. 9 U.S.C. § 4 states in pertinent part, "A party aggrieved by the alleged ... refusal of another to arbitrate under a written agreement for arbitration may petition any United States district court ... for an order directing that such arbitration proceed in the manner provided for in such agreement.”
.9 U.S.C. § 3 states:
If any suit or proceeding be brought in any of the courts of the United States upon any issue referable to arbitration under an agreement in writing for such arbitration, the court in which such suit is pending, upon being satisfied that the issue involved in such suit or proceeding is referable to arbitration under such an agreement, shall on application of one of the parties stay the trial of the action until such arbitration has *1200 been had in accordance with the terms of the agreement, providing the applicant for the stay is not in default in proceeding with such arbitration.
. In her memorandum in opposition to Sun-Trust’s motion to compel arbitration, Krinsk also claimed that the Loan Agreement’s arbitration and class-action-waiver clauses were unconscionable.
. Because the district court held that Sun-Trust had waived its right to compel arbitration, it did not address Krinsk’s claim that the Loan Agreement’s arbitration and class-action-waiver clauses were unconscionable. That issue, consequently, is not presented on appeal.
. ’’[T]he Supreme Court has commanded that 'questions of arbitrability must be addressed with a healthy regard for the federal policy favoring arbitration.’ ”
Ivax Corp. v. B. Braun of Am., Inc.,
. In
Bonner v. City of Prichard,
. Because federal policy strongly favors arbitration, the party who argues waiver “bears a heavy burden of proof' under this two-part test.
Stone v. E.F. Hutton & Co.,
. For example, the court highlighted that Krinsk was required to respond to SunTrust’s opposition to certification of her original proposed class, which resulted in Krinsk having to file multiple motions to compel discovery.
. We have jurisdiction under 28 U.S.C. § 1292(a)(1).
. We review this legal conclusion by the district court
de novo. See, e.g., Ivax Coif.,
. As SunTrust points out in its brief on appeal, the language of the amended class definition presumably opens the door to allow in class members whose HELOC rights were suspended for, among other things, “monetary defaults, for failing to provide updated financial information, for a material change in financial circumstances, or for a significant decline in the appraised value of the collateral property over [the] three and a half year plus [class period].”
. The only action that SunTrust took after the Amended Complaint was filed was to submit its answer and its motion to compel arbitration thirteen days later. Thus, in no way did SunTrust act in a manner inconsistent with its right to elect arbitration following the filing of the Amended Complaint.
. We are mindful that the district court, on remand, must resolve Krinsk's claim that the Loan Agreement's arbitration and class-action-waiver clauses are unconscionable.
