Exhibit 2.20





VIDEOTRON LTD. / VIDÉOTRON LTÉE





NINTH
SUPPLEMENTAL INDENTURE

Dated as of November 4th, 2011





Wells Fargo Bank, National Association,

Trustee











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NINTH SUPPLEMENTAL INDENTURE, dated as of November 4th, 2011 (this Ninth Supplemental Indenture), by and
among Videotron Ltd. / Vidéotron Ltée, a corporation under the laws of the Province of Québec (the Corporation), 9253-2233 Québec Inc., a corporation under the laws of the Province of Québec
(2233), 9253-2456 Québec Inc., a corporation under the laws of the Province of Québec (2456 and, together with 2233, the Additional Subsidiary Guarantors and each an
Additional Subsidiary Guarantor) and Wells Fargo Bank, National Association, as trustee (the Trustee), to the Indenture, dated as of September 16, 2005, as supplemented through the date hereof (the
Indenture), by and among the Corporation, each of the subsidiary guarantors party thereto (collectively referred to as the Original Subsidiary Guarantors), and the Trustee.

WHEREAS, the Corporation, the Original Subsidiary Guarantors and the Trustee have entered into the Indenture
governing the Corporations 6 3/8% Senior
Notes due December 15, 2015 (the Notes);

WHEREAS, Section 4.19 of the Indenture provides
that under certain circumstances the Corporation shall cause a Restricted Subsidiary to execute and deliver to the Trustee a supplemental indenture providing for a Subsidiary Guarantee of the payment of the Notes by such Restricted Subsidiary;

WHEREAS, the parties hereto are desirous of further supplementing the Indenture in the manner hereinafter provided for the
purpose of providing Subsidiary Guarantees by each of the Additional Subsidiary Guarantors in accordance with the terms of the Indenture;

WHEREAS, Section 9.01(e) of the Indenture provides that the Corporation and the Trustee may amend or supplement the Indenture without the consent of any Holder to add additional guarantees with
respect to the Notes; and

WHEREAS, all things necessary have been done to make this Ninth Supplemental Indenture a valid
agreement of the Corporation, each of the Additional Subsidiary Guarantors and the Trustee, in accordance with its terms.

NOW, THEREFORE,
THIS NINTH SUPPLEMENTAL INDENTURE WITNESSETH:

For and in consideration of the premises contained herein, the parties hereto
mutually covenant and agree as follows:

1. Terms used in this Ninth Supplemental Indenture that are not defined herein shall
have the meanings set forth in the Indenture.

2. Each of the Additional Subsidiary Guarantors hereby agrees to provide an
unconditional Subsidiary Guarantee on the terms and subject to the conditions and limitations set forth in the Indenture, including but not limited to Article 10 of the Indenture.

3. This Ninth Supplemental Indenture shall be construed as supplemental to the Indenture and shall form a part thereof, and the Indenture
is hereby incorporated by reference herein and, as supplemented, modified and restated hereby, is hereby ratified, approved and confirmed.



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4. This Ninth Supplemental Indenture shall be effective as of the date hereof. On and after
the date hereof, each reference in the Indenture to this Indenture, hereunder, hereof, or herein shall mean and be a reference to the Indenture as supplemented by this Ninth Supplemental Indenture
unless the context otherwise requires.

5. Except as provided below, in the event of a conflict between the terms and
conditions of the Indenture and the terms and conditions of this Ninth Supplemental Indenture, the terms and conditions of this Ninth Supplemental Indenture shall prevail.

6. If any provision of this Ninth Supplemental Indenture limits, qualifies or conflicts with another provision of the Indenture that is required to be included by the Trust Indenture Act of 1939, as
amended (the Act), as in force at the date this Ninth Supplemental Indenture is executed, the provision required by said Act shall control.

7. This Ninth Supplemental Indenture shall be governed and construed in accordance with the laws of the State of New York.

8. This Ninth Supplemental Indenture may be signed in any number of counterparts with the same effect as if the signatures to each counterpart were upon a single instrument, and all such counterparts
together shall be deemed an original of this Ninth Supplemental Indenture.

9. The recitals contained in this Ninth
Supplemental Indenture shall be taken as the statements of the Corporation, and the Trustee assumes no responsibility for their correctness. The Trustee makes no representations as to the validity or sufficiency of this Ninth Supplemental Indenture.

[SIGNATURES ON FOLLOWING PAGES]



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IN WITNESS WHEREOF, the parties hereto have caused this Ninth Supplemental Indenture to be
duly executed as of the day and year first above written.

CORPORATION:



|               |  |                     |  |  |  |     |  |                           
|-------------- |  | ------------------- |  |  |  | --- |  | --------------------------
|VIDÉOTRON LTÉE
|               |  |                     |  | 
|By:            |  | /s/ Chloé Poirier   |  |  |  | By: |  | /s/ Christian Marcoux     
|               |  | Name: Chloé Poirier |  |  |  |     |  | Name: Christian Marcoux   
|               |  | Title: Treasurer    |  |  |  |     |  | Title: Assistant Secretary

ADDITIONAL SUBSIDIARY GUARANTOR:



|                      |  |                     |  |  |  |     |  |                           
|--------------------- |  | ------------------- |  |  |  | --- |  | --------------------------
|9253-2233 QUÉBEC INC.
|                      |  |                     |  | 
|By:                   |  | /s/ Chloé Poirier   |  |  |  | By: |  | /s/ Christian Marcoux     
|                      |  | Name: Chloé Poirier |  |  |  |     |  | Name: Christian Marcoux   
|                      |  | Title: Treasurer    |  |  |  |     |  | Title: Assistant Secretary

ADDITIONAL SUBSIDIARY GUARANTOR:



|                      |  |                     |  |  |  |     |  |                           
|--------------------- |  | ------------------- |  |  |  | --- |  | --------------------------
|9253-2456 QUÉBEC INC.
|                      |  |                     |  | 
|By:                   |  | /s/ Chloé Poirier   |  |  |  | By: |  | /s/ Christian Marcoux     
|                      |  | Name: Chloé Poirier |  |  |  |     |  | Name: Christian Marcoux   
|                      |  | Title: Treasurer    |  |  |  |     |  | Title: Assistant Secretary

TRUSTEE:



|                                       |  |                           |  |  |  |     |  |                      
|-------------------------------------- |  | ------------------------- |  |  |  | --- |  | ---------------------
|WELLS FARGO BANK, NATIONAL ASSOCIATION
|                                       |  |                           |  | 
|By:                                    |  | /s/ Raymond Delli Colli   |  |  |  | By: |  | /s/ Martin Reed      
|                                       |  | Name: Raymond Delli Colli |  |  |  |     |  | Name: Martin Reed    
|                                       |  | Title: Vice President     |  |  |  |     |  | Title: Vice President

Ninth Supplemental Indenture to 2005 Indenture