Exhibit 99.1

EXECUTION COPY

FIRST AMENDMENT TO RESTRUCTURING SUPPORT AGREEMENT

This First Amendment to Restructuring Support Agreement (this “First Amendment”) is entered into as of December 9, 2011, by and among Dynegy Inc. (“DI”), Dynegy Holdings, LLC (“DH”), on behalf of itself and certain of its subsidiaries (collectively, the “Company”)(1) and the undersigned, each as a Consenting Noteholder (as defined in the Noteholder Support Agreement (defined below)) (collectively, the “Parties”).

W I T N E S S E T H

WHEREAS, reference is made to that certain Restructuring Support Agreement, dated as of November 7, 2011, by and among the Parties (the “Noteholder Support Agreement”); and

WHEREAS, the Parties desire to amend the Noteholder Support Agreement in accordance with Section 20 of the Noteholder Support Agreement.

NOW, THEREFORE, in consideration of the covenants and agreements herein contained and other good and valuable consideration (the receipt and sufficiency of which are hereby acknowledged), the Parties hereby covenant and agree as follows:

1.             Capitalized terms used herein and not otherwise defined herein shall have the respective meanings ascribed to such terms in the Noteholder Support Agreement.

2.             Section 1 of the Noteholder Support Agreement shall be amended as follows:

(a)           The definition of “New Convertible Notes Indentures” shall be deleted in its entirety.

(b)           The following new definition will be added immediately after the definition of “Business Day”:

“Certificate of Designation” means that certain Certificate of Designation of Dynegy Inc., pursuant to Section 151 of the General Corporation Law of the State of Delaware, to be dated as of the Effective Date, governing the Series A Redeemable Convertible Preferred Stock, which shall be consistent in all material respects with the Restructuring Term Sheet and otherwise in form and substance reasonably acceptable to DI, the Company and a Majority of the Consenting Noteholders.

(c)           The definition of “Plan Related Documents” shall be amended to change “New Convertible Notes Indenture” to “Certificate of Designation”.

(1)  Specifically, the term “Company” as used in this First Amendment consists of the following entities, each of which is a debtor under Chapter 11 of the Bankruptcy Code:  Dynegy Holdings, LLC, Dynegy Northeast Generation, Inc., Hudson Power, L.L.C., Dynegy Danskammer, L.L.C. and Dynegy Roseton, L.L.C.

3.             Section 6 of the Noteholder Support Agreement shall be amended as follows:

(a)           “December 7, 2011” shall be changed to “December 14, 2011”;

(b)           The language in the sixth line referring to “three (3) Business Days’ prior notice” shall be changed to “two (2) Business Days’ prior notice”; and

(c)           The following proviso shall be added in the seventh line, immediately prior to the existing proviso:  “provided, however, that for purposes of this Section 6, solely in connection with the Documentation Milestone, “Plan Related Documents” shall not include (i) the Confirmation Order, (ii) the New Secured Notes Indenture (other than the Description of Notes in connection therewith), and (iii) those appendices, amendments, modifications, supplements, exhibits and schedules to the Plan or Disclosure Statement that DI, DH and a Majority of the Consenting Noteholders agree may be filed later.”

4.             Other than as expressly amended by this First Amendment (which First Amendment shall only be effective as to the Parties who execute it), the Noteholder Support Agreement remains in full force and effect in accordance with its original terms.

5.             This First Amendment shall be governed by and construed in accordance with the laws of the State of New York, without regard to the conflict of laws principles thereof.  Any action brought in connection with this First Amendment shall be brought in the Bankruptcy Court, and the Parties hereby irrevocably consent to the jurisdiction of such court and waive any objections as to venue or inconvenient forum.

6.             All modifications and amendments to this First Amendment or any part hereof must be in writing signed by or on behalf of DI, DH and a Majority of the Consenting Noteholders and any waiver of any breach or provision of this First Amendment must be signed by the Parties waiving such breach or provision.

7.             This First Amendment may be executed in counterparts and signature pages exchanged by facsimile or by other electronic form, and each counterpart shall be deemed to be an original, but both counterparts of which shall constitute the same agreement.

8.             Each person who executes this First Amendment on behalf of a Party represents that he or she is duly authorized to execute this First Amendment on behalf of such party.

9.             This First Amendment is not and shall not be deemed to be a solicitation of votes for the acceptance of the Plan (or any other plan of reorganization) for the purposes of sections 1125 and 1126 of the Bankruptcy Code or otherwise.

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IN WITNESS WHEREOF, the Parties have caused this First Amendment to be executed as of the date above written.