Exhibit 4.3

SECOND SUPPLEMENTAL INDENTURE
SUBSIDIARY GUARANTEES

SECOND SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as of March 29, 2024, among the subsidiary guarantors listed on Schedule I hereto (the “Guaranteeing Subsidiaries”), Vistra Operations Company LLC, a Delaware limited liability company (the “Company”), the other subsidiary guarantors party hereto and Wilmington Trust, National Association, as trustee under the indenture referred to below (the “Trustee”).

W I T N E S S E T H

WHEREAS, the Company has heretofore executed and delivered to the Trustee that certain Indenture (as supplemented and amended, the “Indenture”), dated as of September 26, 2023, among the Company, the Subsidiary Guarantors party thereto and the Trustee, providing for the issuance of an aggregate principal amount of $1,450,000,000 of 7.750% Senior Notes due 2031 (the “Notes”);

WHEREAS, the Indenture provides that under certain circumstances the Guaranteeing Subsidiaries shall execute and deliver to the Trustee a supplemental indenture pursuant to which the Guaranteeing Subsidiaries shall unconditionally guarantee all of the Company’s Obligations under the Notes and the Indenture (the “Subsidiary Guarantees”); and

WHEREAS, pursuant to Sections 4.07 and 9.01 of the Indenture, the Trustee, the Company and the other Subsidiary Guarantors are authorized and required to execute and deliver this Supplemental Indenture.

NOW THEREFORE, in consideration of the foregoing and for good and valuable consideration, the receipt of which is hereby acknowledged, the Guaranteeing Subsidiaries, the Trustee, the Company and the other Subsidiary Guarantors mutually covenant and agree for the equal and ratable benefit of the Holders of the Notes as follows:

1. Capitalized Terms. Unless otherwise defined in this Supplemental Indenture, capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture.

2. Agreement to be Bound; Guarantee. The Guaranteeing Subsidiaries hereby become a party to the Indenture as a Subsidiary Guarantor and as such will have all of the rights and be subject to all of the Obligations and agreements of a Subsidiary Guarantor under the Indenture. The Guaranteeing Subsidiaries hereby agree to be bound by all of the provisions of the Indenture applicable to a Subsidiary Guarantor and to perform all of the Obligations and agreements of a Subsidiary Guarantor under the Indenture. In furtherance of the foregoing, each Guaranteeing Subsidiary shall be deemed a Subsidiary Guarantor for purposes of Article 10 of the Indenture, including, without limitation, Section 10.02 thereof.

3. NEW YORK LAW TO GOVERN. THIS SUPPLEMENTAL INDENTURE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK.

4. Counterparts. The parties may sign any number of copies of this Supplemental Indenture. Each signed copy shall be an original, but all of them together represent the same agreement.

5. Effect of Headings. The Section headings herein are for convenience only and shall not affect the construction hereof.

6. The Trustee. The Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Guaranteeing Subsidiaries and the Company.

7. Ratification of Indenture; Supplemental Indenture Part of Indenture. Except as expressly amended hereby, the Indenture is in all respects ratified and confirmed and all the terms, conditions and provisions thereof shall remain in full force and effect. This Supplemental Indenture shall form a part of the Indenture for all purposes, and every Holder of Notes heretofore or hereafter authenticated and delivered shall be bound hereby.

[Signature Page Follows]

2

IN WITNESS WHEREOF, the parties hereto have caused this Supplemental Indenture to be duly executed and attested, all as of the date first above written.

Dated: March 29, 2024

VISTRA VISION HOLDINGS I LLC

VISTRA VISION MANAGEMENT LLC

PULASKI SOLAR, LLC

MASSAC TRANSMISSION, LLC,

as the Guaranteeing Subsidiaries

By:    /s/ William M. Quinn    

Name:    William M. Quinn

Title:    Senior Vice President and Treasurer

VISTRA OPERATIONS COMPANY LLC,

as the Company

By:    /s/ William M. Quinn    

Name:    William M. Quinn

Title:    Senior Vice President and Treasurer

Bellingham Power Generation LLC

Big Brown Power Company LLC

Blackstone Power Generation LLC

Calumet Energy Team, LLC

Casco Bay Energy Company, LLC

Coffeen and Western Railroad Company

Coleto Creek Power, LLC

Coleto Creek Energy Storage LLC

Dallas Power & Light Company, Inc.

Dicks Creek Power Company LLC

Dynegy Coal Holdco, LLC

Dynegy Coal Trading & Transportation, L.L.C.

Dynegy Conesville, LLC

Dynegy Killen, LLC

Dynegy Marketing and Trade, LLC

Dynegy Midwest Generation, LLC

Dynegy Operating Company

Dynegy Power Marketing, LLC

Dynegy Resources Generating Holdco, LLC

Dynegy South Bay, LLC

Dynegy Stuart, LLC

Ennis Power Company, LLC

EquiPower Resources Corp.

[Signature Page to Second Supplemental Indenture]

Fayette Power Company LLC

Generation SVC Company

Hanging Rock Power Company LLC

Hays Energy, LLC

Hopewell Power Generation, LLC

Illinois Power Generating Company

Illinois Power Resources Generating, LLC

Illinois Power Resources, LLC

Illinova Corporation

IPH, LLC

Kendall Power Company LLC

Kincaid Generation, L.L.C.

La Frontera Holdings, LLC

Lake Road Generating Company, LLC

Liberty Electric Power, LLC

Lone Star Energy Company, Inc.

Lone Star Pipeline Company, Inc.

Luminant Administrative Services Company

Luminant Coal Generation LLC

Luminant Commercial Asset Management LLC

Luminant Energy Company LLC

Luminant Energy Trading California Company

Luminant ET Services Company LLC

Luminant Gas Imports LLC

Luminant Generation Company LLC

Luminant Mining Company LLC

Luminant Power Generation, LLC

Luminant Power LLC

Maroon Farmer, LLC

Masspower, LLC

Miami Fort Power Company LLC

Midlothian Energy, LLC

Milford Power Company, LLC

Morro Bay Energy Storage 1, LLC

Morro Bay Energy Storage 2, LLC

Morro Bay Power Company LLC

Moss Landing Energy Storage 4, LLC

Moss Landing Power Company LLC

NCA Resources Development Company LLC

NEPCO Services Company

Northeastern Power Company

Oak Grove Management Company LLC

Oakland Energy Storage 2, LLC

Oakland Energy Storage 3, LLC

Oakland Power Company LLC

Ontelaunee Power Operating Company, LLC

Pleasants Energy, LLC

Sandow Power Company LLC

Sayreville Power Generation LP

[Signature Page to Second Supplemental Indenture]

Sayreville Power GP Inc.

Sayreville Power Holdings LLC

Sithe Energies, Inc.

Sithe/Independence LLC

Southwestern Electric Service Company, Inc.

Texas Electric Service Company, Inc.

Texas Energy Industries Company, Inc.

Texas Power & Light Company, Inc.

Texas Utilities Company, Inc.

Texas Utilities Electric Company, Inc

Trinidad Power Storage LLC

TXU Electric Company, Inc.

Vistra Asset Company LLC

Vistra Corporate Services Company

Vistra EP Properties Company

Vistra Finance Corp.

Vistra Insurance Solutions LLC

VZ Development LLC

Washington Power Generation LLC

Wise County Power Company, LLC

Wise-Fuels Pipeline, Inc.

Zimmer Power Company LLC, as Subsidiary Guarantors

By:    /s/ William M. Quinn    

Name:    William M. Quinn

Title:    Senior Vice President and Treasurer

[Signature Page to Second Supplemental Indenture]

WILMINGTON TRUST, NATIONAL ASSOCIATION,
as the Trustee

By:    /s/ Latoya S Elvin    

Name:    Latoya S Elvin

Title:    Vice President

[Signature Page to Second Supplemental Indenture]

SCHEDULE I

GUARANTEEING SUBSIDIARIES

Name	Jurisdiction
VISTRA VISION HOLDINGS I LLC	Delaware
VISTRA VISION MANAGEMENT LLC	Delaware
PULASKI SOLAR, LLC	Delaware
MASSAC TRANSMISSION, LLC	Delaware