Document:

EX-4.52

 Exhibit 4.52 

FIRST SUPPLEMENTAL INDENTURE 
 TO
BE DELIVERED IN CONNECTION WITH THE VISTRA ACQUISITION 
 FIRST SUPPLEMENTAL INDENTURE (this “Supplemental Indenture”), dated as
of April 9, 2018, between Vistra Energy Corp., a Delaware corporation (the “Successor”), the Subsidiary Guarantors (as defined in the Indenture referred to herein) and Wilmington Trust, National Association, as trustee under the
indenture referred to below (the “Trustee”). Unless otherwise defined in this Supplemental Indenture, capitalized terms used herein without definition shall have the meanings assigned to them in the Indenture (as defined below). 

WITNESSETH 
 WHEREAS, Dynegy Inc.
(“Dynegy”) has heretofore executed and delivered to the Trustee an indenture (as supplemented from time to time prior to the date hereof, the “Indenture”), dated as of August 21, 2017, among Dynegy, the Subsidiary Guarantors
named therein and the Trustee, providing for the original issuance of an aggregate principal amount of $850,000,000 of 8.125% Senior Notes due 2026 and, subject to the terms of the Indenture, future unlimited issuances of 8.125% Senior Notes due
2026 (the “2026 Notes”); 
 WHEREAS, the Successor has filed with the Secretary of State of the State of Delaware a Certificate of
Merger, dated as of April 9, 2018, which provides for the merger of Dynegy with and into the Successor (the “Merger”), with the Successor continuing its corporate existence under the laws of the State of Delaware as the surviving
company of the Merger; 
 WHEREAS, Section 5.01 of the Indenture provides, among other things, that Dynegy may consolidate or merge
with or into another Person; provided that, among other things, the Person formed by or surviving any such consolidation or merger (if other than Dynegy) assumes all the obligations of Dynegy under the Indenture, the 2026 Notes and the Registration
Rights Agreement, dated as of August 21, 2017, among Dynegy, the Subsidiary Guarantors and the other parties named on the signature pages thereto (the “Registration Rights Agreement”) pursuant to a supplemental indenture; 

WHEREAS, Section 9.01 of the Indenture provides, among other things, that the Indenture and the 2026 Notes may be amended or supplemented
without the consent of any Holder to provide for the assumption of Dynegy’s obligations to Holders of the 2026 Notes in the case of a merger or consolidation; and 

WHEREAS, the Successor desires and has requested that the Trustee join in the execution of this Supplemental Indenture for the purpose of
evidencing such assumption by the Successor. 

  
 1 

 NOW THEREFORE, in consideration of the foregoing and for good and valuable consideration, the
receipt of which is hereby acknowledged, the Trustee and the Successor mutually covenant and agree for the equal and ratable benefit of the Holders of the 2026 Notes as follows: 

ARTICLE 1 
 ASSUMPTION AND
AGREEMENTS 
 Section 1.1. The Successor hereby, in accordance with the terms and conditions of the Indenture,
assumes the due and punctual payment of the principal of, premium, if any, and interest and Special Interest, if any, on the 2026 Notes, and the due and punctual performance and observance of all other covenants, conditions and other obligations
contained in the Indenture, the 2026 Notes and the Registration Rights Agreement on the part of Dynegy to be performed or observed. 

Section 1.2. The Successor shall succeed to, and be substituted for, and may exercise every right and power of,
Dynegy under the Indenture, the 2026 Notes and the Registration Rights Agreement with the same effect as if the Successor had been named as “the Company” therein. 

ARTICLE 2 
 MISCELLANEOUS 

Section 2.1. NEW YORK LAW TO GOVERN. THE INDENTURE, THIS SUPPLEMENTAL INDENTURE AND THE 2026 NOTES SHALL BE GOVERNED
BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK. 
 Section 2.2. 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. 

Section 2.3. Effect of Headings. The Section headings herein are for convenience only and shall not affect the
construction hereof. 
 Section 2.4. 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 Successor. 

Section 2.5. 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 the 2026 Notes heretofore or hereafter authenticated and delivered shall be bound hereby. 
 [Signature pages follow] 

  
 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. 
  

			
	 VISTRA ENERGY CORP., as Successor

		
	By:	 	 /s/ Kristopher E. Moldovan

	Name:	 	Kristopher E. Moldovan
	Title:	 	Senior Vice President and Treasurer

 ANP BELLINGHAM ENERGY COMPANY, LLC 

ANP BLACKSTONE ENERGY COMPANY, LLC 
 CALUMET ENERGY
TEAM, LLC 
 CASCO BAY ENERGY COMPANY, LLC 

COFFEEN AND WESTERN RAILROAD COMPANY 
 DYNEGY
ADMINISTRATIVE SERVICES COMPANY 
 DYNEGY ASSOCIATES NORTHEAST LP, INC. 

DYNEGY COAL GENERATION, LLC 
 DYNEGY COAL HOLDCO, LLC

 DYNEGY COAL TRADING & TRANSPORTATION, L.L.C. 

DYNEGY COMMERCIAL ASSET MANAGEMENT, LLC 
 DYNEGY
CONESVILLE, LLC 
 DYNEGY DICKS CREEK, LLC 

DYNEGY ENERGY SERVICES (EAST), LLC 
 DYNEGY ENERGY
SERVICES, LLC 
 DYNEGY FAYETTE II, LLC 
 DYNEGY
GAS IMPORTS, LLC 
 DYNEGY GLOBAL LIQUIDS, INC. 

DYNEGY HANGING ROCK II, LLC 
 DYNEGY KENDALL ENERGY, LLC

 DYNEGY KILLEN, LLC 
 DYNEGY MARKETING AND
TRADE, LLC 
 DYNEGY MIAMI FORT, LLC 
 DYNEGY
MIDWEST GENERATION, LLC 
 DYNEGY MORRO BAY, LLC 

DYNEGY MOSS LANDING, LLC 
 DYNEGY NORTHEAST GENERATION
GP, INC. 
 DYNEGY OAKLAND, LLC 
 DYNEGY OPERATING
COMPANY 
 DYNEGY POWER GENERATION INC. 
 DYNEGY
POWER MARKETING, LLC 
 DYNEGY POWER, LLC 

[Signature Page to 2026 Notes Supplemental Indenture] 

 DYNEGY RESOURCE II, LLC 

DYNEGY RESOURCES GENERATING HOLDCO, LLC 
 DYNEGY SOUTH
BAY, LLC 
 DYNEGY STUART, LLC 
 DYNEGY WASHINGTON
II, LLC 
 DYNEGY ZIMMER, LLC 
 EQUIPOWER
RESOURCES CORP. 
 HAVANA DOCK ENTERPRISES, LLC 

HOPEWELL POWER GENERATION, LLC 
 ILLINOIS POWER
GENERATING COMPANY 
 ILLINOIS POWER MARKETING COMPANY 

ILLINOIS POWER RESOURCES GENERATING, LLC 
 ILLINOIS
POWER RESOURCES, LLC 
 ILLINOVA CORPORATION 

IPH, LLC 
 IPH II, LLC 

KINCAID GENERATION, L.L.C. 
 LAKE ROAD GENERATING
COMPANY, LLC 
 LIBERTY ELECTRIC POWER, LLC 

MASSPOWER, LLC 
 MILFORD POWER COMPANY, LLC 

NEPCO SERVICES COMPANY 
 NORTHEASTERN POWER COMPANY

 ONTELAUNEE POWER OPERATING COMPANY, LLC 

PLEASANTS ENERGY, LLC 
 RICHLAND-STRYKER GENERATION, LLC

 SITHE ENERGIES, INC. 
 SITHE/INDEPENDENCE LLC,

 as Subsidiary Guarantors 
  

			
	By:	 	 /s/ Kristopher E. Moldovan

	Name:	 	Kristopher E. Moldovan
	Title:	 	Senior Vice President and Treasurer

 [Signature Page to 2026 Notes Supplemental Indenture] 

			
	 WILMINGTON TRUST, NATIONAL

ASSOCIATION, 
 as
Trustee

		
	By:	 	 /s/ Shawn Goffinet

	Name:	 	Shawn Goffinet
	Title:	 	Assistant Vice President

 [Signature Page to 2026 Notes Supplemental Indenture]EX-10.10

 Exhibit 10.10 

Execution Version 

ASSUMPTION AGREEMENT 

ASSUMPTION AGREEMENT dated as of April 9, 2018 (this “Assumption Agreement”), between VISTRA ENERGY CORP., a Delaware
corporation (the “New Borrower”) (as successor by merger to DYNEGY INC., a Delaware Corporation, “Dynegy”), and CREDIT SUISSE AG, CAYMAN ISLANDS BRANCH, (“Credit Suisse”), as
Administrative Agent (in such capacity, the “Administrative Agent”) and as collateral trustee (in such capacity, the “Collateral Trustee”) for the First-Lien Secured Parties (as defined therein). 

WHEREAS, Dynegy, the lenders named therein (the “Lenders”), and Credit Suisse, as Administrative Agent (in such
capacity, the “Administrative Agent”) and Collateral Trustee for the Lenders are party to that certain Credit Agreement, dated as of April 23, 2013 (as amended, restated, amended and restated, replaced, supplemented and/or otherwise
modified from time to time, the “Credit Agreement”; capitalized terms used but not otherwise defined herein having the meanings assigned to such terms in the Credit Agreement); 

WHEREAS, pursuant to the agreement and plan of merger dated as of October 29, 2017 (the “Merger Agreement”),
between the New Borrower and Dynegy, Dynegy will merge with and into the New Borrower, with the New Borrower as the surviving entity of such merger; 

WHEREAS, Section 10.02 of the Credit Agreement provides that any Person formed by or surviving a consolidation or merger with the
Borrower (if other than the Borrower) shall assume all obligations of the Borrower under the Credit Documents pursuant to joinder agreements or other documents and agreements reasonably satisfactory to the Administrative Agent. 

WHEREAS, the New Borrower is executing and delivering this Assumption Agreement in accordance with the requirements of the Credit Agreement of
Section 10.02 of the Credit Agreement to become a Borrower under the Credit Agreement; 
 Accordingly, the New Borrower, the
Administrative Agent and Collateral Trustee agree as follows: 
 SECTION 1. In accordance with Section 10.02 of the Credit Agreement,
the New Borrower by its signature below becomes the “Borrower” under the Credit Agreement and each of the other Credit Documents with the same force and effect as if originally named therein as the Borrower and the New Borrower hereby
agrees to all the terms and provisions of the Credit Agreement and each of the other Credit Documents applicable to it as Borrower thereunder, agrees to be bound by the terms of the Credit Agreement, as the Borrower thereunder (including, without
limitation, the covenants set forth therein) and assumes all obligations (including without limitation, all payment obligations), rights and powers of a Borrower thereunder. Each reference to the “Borrower” in the Credit
Agreement and each of the other Credit Documents shall be deemed to include the New Borrower. The Credit Agreement is hereby incorporated herein by reference. 

SECTION 2. The New Borrower represents and warrants to the Administrative Agent, the Collateral Trustee, the Lenders and the other First-Lien
Secured Parties that this Assumption Agreement has been duly authorized, executed and delivered by it and constitutes its 

 
legal, valid and binding obligation, enforceable against it in accordance with its terms except to the extent that enforceability thereof may be limited by applicable bankruptcy, insolvency,
reorganization or similar laws affecting the enforcement of creditors’ rights generally or by general principles of equity (regardless of whether such enforcement is considered in a proceeding in equity or at law). 

SECTION 3. The New Borrower represents and warrants that immediately after giving effect to the merger of Dynegy with and into the New
Borrower, no Default or Event of Default exists and the Fixed Charge Coverage Ratio of the New Borrower is greater, after giving pro forma effect, to the merger of Dynegy with and into the New Borrower and any related financing transactions as if
the same had occurred at the beginning of the applicable Test Period than the Borrower’s actual Fixed Charge Coverage Ratio for the period. 

SECTION 4. This Assumption Agreement may be executed in any number of counterparts and by the different parties hereto on separate
counterparts, each of which when so executed and delivered shall be an original, but all of which shall together constitute one and the same instrument. Delivery of a counterpart via facsimile or other electronic transmission shall constitute
delivery of an original counterpart. A set of counterparts executed by all the parties hereto shall be lodged with the Borrower, the Administrative Agent and the Collateral Trustee. 

SECTION 5. This Assumption Agreement shall constitute notice for the purposes of and satisfy the obligation, with respect to the New Borrower,
under Section 4.03 of that certain Guarantee and Collateral Agreement, dated as of April 23, 2013 (as amended, restated, amended and restated, replaced supplemented and/or otherwise modified from time to time) among the New Borrower (as
successor by merger to Dynegy), each Restricted Subsidiary (as defined in the Credit Agreement) of the New Borrower from time to time party thereto and Credit Suisse as Collateral Trustee. 

SECTION 6. Except as expressly supplemented hereby, the Credit Agreement shall remain in full force and effect. 

SECTION 7. (a)    THIS ASSUMPTION AGREEMENT AND THE OTHER CREDIT DOCUMENTS AND THE RIGHTS AND OBLIGATIONS OF
THE PARTIES HEREUNDER AND THEREUNDER SHALL, EXCEPT AS OTHERWISE PROVIDED IN ANY MORTGAGE, BE CONSTRUED IN ACCORDANCE WITH AND BE GOVERNED BY THE LAW OF THE STATE OF NEW YORK WITHOUT REGARD TO PRINCIPLES OF CONFLICT OF LAWS TO THE EXTENT THAT
THE SAME ARE NOT MANDATORILY APPLICABLE BY STATUTE AND WOULD REQUIRE OR PERMIT THE APPLICATION OF THE LAW OF ANOTHER JURISDICTION. ANY LEGAL ACTION OR PROCEEDING WITH RESPECT TO THIS ASSUMPTION AGREEMENT OR ANY OTHER CREDIT DOCUMENTS MAY BE BROUGHT
IN THE COURTS OF THE STATE OF NEW YORK OR OF THE UNITED STATES FOR THE SOUTHERN DISTRICT OF NEW YORK, IN EACH CASE WHICH ARE LOCATED IN THE COUNTY OF NEW YORK, AND, BY EXECUTION AND DELIVERY OF THIS ASSUMPTION AGREEMENT OR ANY OTHER CREDIT
DOCUMENTS, EACH PARTY HERETO HEREBY IRREVOCABLY ACCEPTS FOR ITSELF AND IN RESPECT OF ITS PROPERTY, GENERALLY AND UNCONDITIONALLY, THE EXCLUSIVE JURISDICTION OF THE AFORESAID COURTS. 

  
 2 

 
EACH PARTY HERETO HEREBY FURTHER IRREVOCABLY WAIVES (TO THE EXTENT PERMITTED BY APPLICABLE LAW) ANY CLAIM THAT ANY SUCH COURTS LACK PERSONAL JURISDICTION OVER SUCH PARTY, AND AGREES NOT TO PLEAD
OR CLAIM, IN ANY LEGAL ACTION PROCEEDING WITH RESPECT TO THIS ASSUMPTION AGREEMENT OR ANY OTHER CREDIT BROUGHT IN ANY OF THE AFOREMENTIONED COURTS, THAT SUCH COURTS LACK PERSONAL JURISDICTION OVER SUCH PARTY. EACH PARTY HERETO FURTHER IRREVOCABLY
CONSENTS TO THE SERVICE OF PROCESS OUT OF ANY OF THE AFOREMENTIONED COURTS IN ANY SUCH ACTION OR PROCEEDING BY THE MAILING OF COPIES THEREOF BY REGISTERED OR CERTIFIED MAIL, POSTAGE PREPAID, TO SUCH PARTY AT ITS ADDRESS SET FORTH OPPOSITE ITS
SIGNATURE BELOW, SUCH SERVICE TO BECOME EFFECTIVE 30 DAYS AFTER SUCH MAILING. EACH PARTY HERETO HEREBY IRREVOCABLY WAIVES (TO THE EXTENT PERMITTED BY APPLICABLE LAW) ANY OBJECTION TO SUCH SERVICE OF PROCESS AND FURTHER IRREVOCABLY WAIVES AND AGREES
NOT TO PLEAD OR CLAIM IN ANY ACTION OR PROCEEDING COMMENCED HEREUNDER OR ANY OTHER CREDIT DOCUMENT THAT SERVICE OF PROCESS WAS IN ANY WAY INVALID OR INEFFECTIVE. NOTHING HEREIN SHALL AFFECT THE RIGHT OF (i) ANY PARTY HERETO TO SERVE PROCESS IN
ANY OTHER MANNER PERMITTED BY LAW OR (ii) THE ADMINISTRATIVE AGENT, ANY LENDER OR THE HOLDER OF ANY NOTE TO COMMENCE LEGAL PROCEEDINGS OR OTHERWISE PROCEED AGAINST ANY GRANTOR IN ANY OTHER JURISDICTION. 

(b)    EACH PARTY HERETO HEREBY IRREVOCABLY WAIVES (TO THE EXTENT PERMITTED BY APPLICABLE LAW) ANY OBJECTION WHICH IT MAY
NOW OR HEREAFTER HAVE TO THE LAYING OF VENUE OF ANY OF THE AFORESAID ACTIONS OR PROCEEDINGS ARISING OUT OF OR IN CONNECTION WITH THIS ASSUMPTION AGREEMENT BROUGHT IN THE COURTS REFERRED TO IN CLAUSE (a) ABOVE AND HEREBY FURTHER IRREVOCABLY
WAIVES AND AGREES NOT TO PLEAD OR CLAIM IN ANY SUCH COURT THAT ANY SUCH ACTION OR PROCEEDING BROUGHT IN ANY SUCH COURT HAS BEEN BROUGHT IN AN INCONVENIENT FORUM. 

(c)    EACH OF THE PARTIES TO THIS ASSUMPTION AGREEMENT HEREBY IRREVOCABLY WAIVES (TO THE EXTENT PERMITTED BY APPLICABLE
LAW) ALL RIGHT TO A TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM ARISING OUT OF OR RELATING TO THIS ASSUMPTION AGREEMENT OR THE TRANSACTIONS CONTEMPLATED HEREBY. 

SECTION 8. In the event any one or more of the provisions contained in this Joinder should be held invalid, illegal or unenforceable in any
respect, the validity, legality and enforceability of the remaining provisions contained herein and therein shall not in any way be affected or impaired thereby (it being understood that the invalidity of a particular provision in a particular
jurisdiction shall not in and of itself affect the validity of such provision in any other jurisdiction). The parties shall endeavor in good-faith negotiations to replace the invalid, illegal or unenforceable provisions with valid provisions the
economic effect of which comes as close as possible to that of the invalid, illegal or unenforceable provisions. 

  
 3 

 SECTION 9. All communications and notices hereunder shall be in writing and given as provided in
Section 13.03 of the Credit Agreement. 
 SECTION 10. The New Borrower agrees to reimburse the Administrative Agent and the Collateral
Trustee for its reasonable and documented out-of-pocket expenses in connection with this Assumption Agreement, including the reasonable fees, other charges and
disbursements of counsel for the Administrative Agent and the Collateral Trustee. 
 [Signature pages follow] 

  
 4 

 IN WITNESS WHEREOF, the undersigned has caused this Assumption Agreement to be duly
executed and delivered by its duly authorized officer as of the date above first written. 
  

			
	VISTRA ENERGY CORP.
		
	By:	 	 /s/ Kristopher E. Moldovan

	Name:	 	Kristopher E. Moldovan
	Title:	 	Senior Vice President and Treasurer

 [Signature Page to Assumption Agreement] 

 CREDIT SUISSE AG, CAYMAN ISLANDS BRANCH, as 

Administrative Agent 
  

			
	By:	 	 /s/ Mikhail Faybusovich

	Name	 	Mikhail Faybusovich
	Title:	 	Authorized Signatory
		
	By:	 	 /s/ Andrew Griffin

	Name	 	Andrew Griffin
	Title:	 	Authorized Signatory

 [Signature Page to Assumption Agreement]

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