Exhibit 10.12.1

Dated 21/12/16

TARGO
Commercial Finance AG

Heinrich-von-Brentano-Str. 2,55130
 Mainz, Germany

and

Constellium Rolled Products Singen GmbH & Co. KG,

Alusingen-Platz 1, 78224 Singen, Germany





AMENDEMENT AGREEMENT

to a Factoring Agreement (dated 27 May 2016)







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This Amendment Agreement (the Agreement) is dated    
November 2016, and entered into between



|(1) | TARGO Commercial Finance AG (previously GE Capital Bank AG),
Heinrich-von-Brentano-Str. 2, 55130 Mainz, Germany, (hereafter referred to as TARGOCF); and
|--- | ----------------------------------------------------------------------------------------------------------------------------------------------------------



|(2) | CONSTELLIUM ROLLED PRODUCTS SINGEN GMBH & CO. KG, registered with the commercial register (Handelsregister) of the local court (Amtsgericht) of Freiburg i.Br., with registration
number HRA 704399, having its registered seat at Alusingen-Platz 1, 78224 Singen, Germany (hereafter referred to as the Originator).
|--- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

TARGOCF and the Originator are hereafter referred to as the Parties.

WHEREAS:



|(1) | TARGOCF as purchaser and the Originator as seller entered into a factoring agreement on 27 May 2016 (as amended and/or restated from time to time), pursuant to which the Originator sells certain receivables to
TARGOCF (the Factoring Agreement).
|--- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------



|(2) | TARGOCF has also entered into a factoring agreement with Constellium Extrusions Deutschland GmbH, a limited liability company, with registered office at Bildstraße 4, 74564 Crailsheim, registered in the commercial
register (Handelsregister) of the local court (Amtsgericht) of Ulm under register number HRB 670619, on 16 December 2010, and has also entered into a factoring agreement with Constellium Valais S.A.., Sierre, a
société anonyme incorporated under the laws of Switzerland with registered address at 3960 Sierre, registered under number CH-626.3.000.048-9., on
16 December 2010, and has also entered into a factoring agreement with Constellium Singen GmbH, a limited liability company, with registered office at Alusingen-Platz 1, 78224 Singen, registered in the commercial register
(Handelsregister) of the local court (Amtsgericht) of Freiburg under register number HRB 540034, on 16 December 2010 (amended and restated on 26 March 2014), and has also entered into a factoring agreement with Constellium
Extrusions Decin s.r.o., a company incorporated and existing under the laws of the Czech Republic, with its registered office at Ústecká 751/37, Děčin V-Rozbělesy, 405 02 Děčin, Czech Republic, identification
number 183 80 654, registered in the Commercial Register maintained by the Regional Court in Ústi nad Labem under file number C 301, on 26 June 2015.
|--- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

TARGOCF and the Originator have agreed to enter into this Agreement in order to amend the Factoring Agreement in accordance with this Agreement.



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|1. | Definitions
|-- | -----------

Terms in italics have the meaning ascribed to them in the Factoring
Agreement, unless otherwise defined herein.



|2. | Amendments to the Factoring Agreement
|-- | -------------------------------------

a) Schedule 1 (Terms and
Conditions) clause 3. a), b) and d) shall be amended and read as follows:



| | 3. | Financing Commission Reference Rate; Fees; Commission:
| | -- | ------------------------------------------------------

a)
Financing Commission Reference Rate (see Clause 4.1): 3 months EURIBOR + 1.20 % p.a., paid monthly and calculated on the last Business Day of each month for the following month.

If the 3 months EURIBOR is 0% or below 0%, the Interest Rate is 1.20 % p.a.

Interest is stated exclusive of applicable VAT.

b) Unused Facility Fee: 0.5% p.a. of the amount of the available but unused amount of the Settlement Account.

d) Factoring Commission and Administration Fee (see Clauses 4.1 and 8.3): 0.095% calculated on the volume of the
Receivables.

b) Schedule 1 (Terms and Conditions) clause 4. shall be amended in whole and read
as follows:

4. Maximum Commitment:

TARGOCF will set a maximum limit for each of Constellium Singen GmbH, Constellium Extrusions Deutschland GmbH, Constellium Valais S.A,
Constellium Extrusions Děčin s.r.o., Constellium Rolled Products Singen GmbH & Co. KG, whereby the total aggregate Maximum Commitment under the respective factoring agreements between TARGOCF and Constellium
Singen GmbH, Constellium Extrusions Deutschland GmbH, Constellium Valais S.A., Constellium Extrusions Děčin s.r.o. and Constellium Rolled Products Singen GmbH & Co. KG amounts to 150.000.000.00 EUR (one hundred fifty million
Euro). The respective Maximum Commitment can be changed upon request of the respective originator(s).

c)
Schedule 1 (Terms and Conditions) clause 6. shall be amended in whole and read as follows:

6.
TerminationDate: 29 October 2021



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In all other respects the provisions of the Factoring Agreement shall remain unaffected.



|3. | PARTIAL INVALIDITY; WAIVER
|-- | --------------------------



|3.1 | Invalidity
|--- | ----------

If any provision of this Agreement should be or become invalid or
unenforceable in whole or in part, this shall not affect the validity or enforceability of the remaining provisions hereof. The invalid or unenforceable provision shall be deemed replaced by that provision which best meets the intent and the
economic purpose of the void or unenforceable provision.



|3.2 | Waiver
|--- | ------

No failure to exercise, nor any delay in exercising, on the part of the
Originator or TARGOCF, any right or remedy hereunder shall operate as a waiver thereof, nor shall any single or partial exercise of any right or remedy prevent any further or other exercise thereof or the exercise of any right or remedy. The rights
and remedies provided hereunder are cumulative and not exclusive of any rights or remedies provided by law.



|4. | Effective Date
|-- | --------------

This Agreement shall become effective immediately once it is executed by
the Parties.



|5. | APPLICABLE LAW; JURISDICTION
|-- | ----------------------------



|5.1 | Applicable Law
|--- | --------------

This Agreement and all obligations arising out of or in connection with
this Agreement shall be governed by and construed in accordance with the laws of the Federal Republic of Germany.



|5.2 | German Courts
|--- | -------------

The courts of Mainz have exclusive jurisdiction to settle any dispute
arising out of or in connection with this Agreement (including a dispute regarding the existence, validity or termination of this Agreement or the consequences of its nullity).



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SIGNATORIES



|                                                 |  |                                        |  |  |  |     
|------------------------------------------------ |  | -------------------------------------- |  |  |  | ----
|TARGO Commercial Finance AG                     
|                                                 |  |                                        | 
|                                                 |  | LOGO                                   |  |  |  | LOGO
|                                                 |  |                                        | 
|Signed by:                                       |  | LOGO                                   |  |  |  | LOGO
|                                                 |  |                                        | 
|Title:                                           |  | LOGO                                   |  |  |  | LOGO
|                                                
|Constellium Rolled Products Singen GmbH & Co. KG
|                                                 |  |                                        | 
|                                                 |  | /s/ MARK KIRKLAND                      |  |  |  |     
|                                                 |  |                                        | 
|Signed by:                                       |  | MARK KIRKLAND                          |  |  |  |     
|Title:                                           |  | GROUP TREASURER & AUTHORISED SIGNATORY |  |  |  |