Exhibit 4.12





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                        FIRST AMENDMENT TO LOAN AGREEMENT



                          Dated as of February 1, 2004

                                     Between

         STATE ENVIRONMENTAL IMPROVEMENT AND ENERGY RESOURCES AUTHORITY



                                       and



                      UNION ELECTRIC COMPANY, DBA AMERENUE
                  ---------------------------------------------
                     Supplementing and amending that certain
                                 Loan Agreement
                          dated as of September 1, 1998


                                   $50,000,000
         State Environmental Improvement and Energy Resources Authority
                Environmental Improvement Revenue Refunding Bonds
                        (Union Electric Company Project)
                                  Series 1998B
                  ---------------------------------------------






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<PAGE>



                        FIRST AMENDMENT TO LOAN AGREEMENT
                            ------------------------


                                TABLE OF CONTENTS

 (This Table of Contents is not a part of the First Amendment to Loan Agreement
                   and is only for convenience of reference.)

<TABLE>
<CAPTION>

SECTION                                                HEADING                                                   PAGE
<S>     <C>               <C>
ARTICLE I                  DEFINITIONS............................................................................2

       Section 1.01.       Definitions of Terms...................................................................2

ARTICLE II                 AMENDMENTS TO ORIGINAL AGREEMENT.......................................................2

       Section 2.01.       Amendment to Article III of the Original Agreement.....................................2
       Section 2.02.       Amendments to Article V of the Original Agreement......................................2
       Section 2.03.       Amendments to Article VI of the Original Agreement.....................................6
       Section 2.04.       Amendment to Section 8.1 of the Original Agreement.....................................7
       Section 2.05.       Amendments to Article IX of the Original Agreement.....................................7
       Section 2.06.       Amendments to Section 10.4 of the Original Agreement...................................8

ARTICLE III                MISCELLANEOUS..........................................................................8

       Section 3.01.       Agreement Confirmed....................................................................8
       Section 3.02.       Severability...........................................................................8
       Section 3.03.       Counterparts...........................................................................8
       Section 3.04.       Applicable Provisions of Law...........................................................8
       Section 3.05.       Effective Date.........................................................................8

</TABLE>

                                       i

<PAGE>



                        FIRST AMENDMENT TO LOAN AGREEMENT

     THIS FIRST AMENDMENT TO LOAN AGREEMENT (this "First Amendment") is made and
entered into as of February 1, 2004 between the STATE ENVIRONMENTAL  IMPROVEMENT
AND ENERGY  RESOURCES  AUTHORITY of the State of Missouri,  a body corporate and
politic  and a  governmental  instrumentality  of the  State  of  Missouri  (the
"Issuer"),  and UNION ELECTRIC COMPANY, a Missouri corporation doing business as
AMERENUE (the "Company"):


                                   WITNESSETH:

     WHEREAS,   on  September  4,  1998  the  Issuer  issued  its  Environmental
Improvement  Revenue  Refunding  Bonds (Union Electric  Company  Project) Series
1998B (the "Bonds") in the original  aggregate  principal  amount of $50,000,000
pursuant to an Indenture  of Trust dated as of September 1, 1998 (the  "Original
Indenture") by and between the Issuer and UMB Bank & Trust,  N.A.,  successor to
State Street Bank and Trust Company of Missouri, N.A. (the "Trustee"); and

     WHEREAS,  in connection with the issuance of the Bonds,  the Issuer and the
Company  executed and delivered the Loan Agreement dated as of September 1, 1998
by and between the Issuer and the Company (the "Original Agreement"); and

     WHEREAS,  the  Original  Indenture  is being  amended  and  restated by the
Amended and Restated  Indenture  of Trust of even date  herewith in order to add
provisions  relating to a bond insurance  policy for the Bonds and to permit the
delivery to the Trustee by the Company of its mortgage  bonds to further  secure
the Bonds; and

     WHEREAS,  Section 11.01 of the Original  Indenture provides that the Issuer
and the Company may,  without notice to or the consent of any Bondholder,  enter
into an  agreement  supplemental  to the  Original  Agreement to make changes in
connection  with any authorized  amendment or supplement to the  Indenture,  and
Section 10.4 of the Original Agreement provides that such supplemental agreement
is subject to the written consent of the Trustee; and

     WHEREAS,  the  Issuer  and the  Company  desire to enter  into  this  First
Amendment,  as permitted by Section 11.01 of the Original  Indenture and Section
10.4 of the Original Agreement, in order to amend the Original Agreement to make
certain  changes  relating  to  the  amendments  being  made  to  the  Indenture
concurrently herewith;

         NOW, THEREFORE, in consideration of the foregoing and of the mutual
covenants herein set forth, the parties hereto agree as follows:

<PAGE>


                                    ARTICLE I

                                   DEFINITIONS

     Section  1.01.  Definitions  of  Terms.  For all  purposes  of  this  First
Amendment, in addition to the terms defined above in the WHEREAS clauses, unless
the context clearly  requires  otherwise,  all terms defined in Article I of the
Indenture have the same meanings in this First Amendment.


                                   ARTICLE II

                        AMENDMENTS TO ORIGINAL AGREEMENT

     Section 2.01. Amendment to Article III of the Original Agreement.  The last
clause of Section 3.5 of the  Original  Agreement  is hereby  amended to read as
follows:

               ",  provided  that the  Trustee  and the Bond  Insurer receive a
               Favorable Opinion of Tax Counsel prior to such abandonment."

     Section  2.02.  Amendments  to  Article V of the  Original  Agreement.  (a)
Subsection  5.1(a)  of the  Original  Agreement  is  hereby  amended  to read as
follows:

                    "(a)  The  Company  will  repay  the  loan  made to it under
               Section 4.1 as follows:  Before the close of business (local time
               at the principal  corporate  office of the  Registrar) on the day
               before  each day on which any payment of either  principal  of or
               interest  on the Bonds,  or both,  shall  become due  (whether at
               maturity,  or upon redemption or acceleration or otherwise),  the
               Company  will pay,  in  immediately  available  funds,  an amount
               which,  together with other moneys held by the Tender Agent or by
               the Trustee  under the Indenture  and  available  therefor,  will
               enable  the  Registrar  to make such  payment in full in a timely
               manner.  If such day on which any payment shall become due is not
               a Business Day,  then the payment  required by this Section shall
               be made on or before the  preceding  Business Day. If the Company
               defaults in any payment  required  by this  Section,  the Company
               will pay interest  (to the extent  allowed by law) on such amount
               until paid at the rate provided for in the Bonds."

     (b) The last  paragraph of Section 5.1 of the Original  Agreement is hereby
amended to read as follows:

                    "All amounts  payable  under this Section by the Company are
               assigned by the Issuer to the Trustee  pursuant to the  Indenture
               for the  benefit of the  Bondholders  and the Bond  Insurer.  The

                                      -2-

<PAGE>


               Company  consents to such  assignment.  Accordingly,  the Company
               will pay  directly to the  Registrar at its  principal  corporate
               trust office all payments payable by the Company pursuant to this
               Section."

     (c) There is hereby added a new  paragraph to the end of Section 5.1 of the
Original Agreement to read as follows:

                    "The  Company  agrees to make all  payments  when due on the
               First  Mortgage  Bonds.  If for any  reason  amounts  paid to the
               Trustee on the First Mortgage  Bonds,  together with other moneys
               held by the Trustee and available for that purpose,  would not be
               sufficient  to make the  corresponding  payments of principal of,
               premium,  if any, and interest on the Bonds corresponding to such
               First Mortgage  Bonds when such payments  become due, the Company
               will pay the  amounts  required  from time to time to make up any
               such deficiency."

     (d) A new  Subsection  5.2(d) is hereby  added to the end of Section 5.2 of
the Original Agreement to read as follows:

                    "(d)  Notwithstanding  any provision herein to the contrary,
               payment  to  the  Bond  Insurer  of all  amounts  due  under  the
               Insurance  Agreement  pursuant  to the  terms  of  the  Insurance
               Agreement."

     (e)  Section 5.3 of the  Original  Agreement  is hereby  amended to read as
follows:

                    "Section  5.3.  Prepayments.  The  Company  may at any  time
               prepay to the  Registrar  all or any part of the amounts  payable
               under  Section 5.1. A prepayment  will not relieve the Company of
               its  obligations  under this Loan  Agreement  until all the Bonds
               have been paid or provision  for the payment of all the Bonds has
               been made in  accordance  with the  Indenture and all amounts due
               the Bond  Insurer  have been  paid.  In the event of a  mandatory
               redemption  of the Bonds,  the  Company  will  prepay all amounts
               necessary for such redemption."

     (f)  Section 5.4 of the  Original  Agreement  is hereby  amended to read as
follows:

                    "Section  5.4.  Obligations  of Company  Unconditional.  The
               Company  agrees that the  obligations  of the Company to make the
               payments  required  by  Sections  5.1 and 5.3 and to perform  its
               other  agreements  contained  in this  Loan  Agreement  shall  be
               absolute and  unconditional.  Until the principal of and interest
               on the Bonds shall have been fully  paid,  or  provision  for the
               payment

                                      -3-

<PAGE>


               of the Bonds made in accordance with the Indenture,  and the Bond
               Insurer  is paid in full,  the  Company  (a) will not  suspend or
               discontinue  any  payments  provided for in Section 5.1, (b) will
               perform all its other  agreements in this Loan  Agreement and (c)
               will not terminate  this Loan  Agreement for any cause  including
               any  acts  or  circumstances   that  may  constitute  failure  of
               consideration,   destruction   of  or  damage  to  the   Project,
               commercial  frustration of purpose, any change in the laws of the
               United  States or of the State or any  political  subdivision  of
               either  or  any  failure  of the  Issuer  to  perform  any of its
               agreements, whether express or implied, or any duty, liability or
               obligation arising from or connected with this Loan Agreement."

     (g) Section 5.5, Section 5.6 and Section 5.7 are hereby added to the end of
Article V of the Original Agreement to read as follows:

                    "Section  5.5.  First  Mortgage  Bonds.  The  Company  shall
               execute  and deliver to the  Trustee,  as assignee of the Issuer,
               its First  Mortgage  Bonds.  The form of the First Mortgage Bonds
               will be substantially as set forth in the Company's  Supplemental
               Indenture to its Mortgage  executed and  delivered to the Trustee
               on the effective date of this First Amendment."

                    "Section  5.6.  Payment  of the Bonds from  Payments  of the
               First Mortgage Bonds and Other Amounts. Payments of principal of,
               and premium, if any, and interest on, the First Mortgage Bonds by
               the Company to the  Trustee,  as  assignee  of the Issuer,  shall
               constitute  payments  of such  amounts on the loan under  Section
               5.1(a)  or of the  purchase  price for the  Bonds  under  Section
               5.1(b).  The Bonds  shall be payable  from  payments  made by the
               Company to the  Trustee of  principal  and  interest on the First
               Mortgage Bonds delivered  hereunder.  Payments of principal of or
               premium,  if any, or interest on, or the purchase  price for, the
               Bonds with moneys held under the Indenture for such payment shall
               be deemed to be like payments with respect to the First  Mortgage
               Bonds.  The obligations of the Company to make payments under the
               First  Mortgage  Bonds  shall  be  absolute  and   unconditional.
               Whenever the Bonds are redeemable in whole or in part, the Issuer
               will  redeem the same upon the  request of the  Company,  and the
               Company  covenants  and  agrees  to pay an  amount  equal  to the
               applicable  redemption  price  of the  Bonds as a  prepayment  of
               principal of and interest due on the First Mortgage Bonds. If the
               Company   prepays  the  First  Mortgage   Bonds,   the  Company's
               obligations under Section 5.1 will be satisfied and there will be
               a  corresponding  redemption  of the Bonds.  Whenever  payment or
               provision  therefor has been made in respect of the  principal of
               or
                                      -4-

<PAGE>

               interest  on all or any portion of the Bonds in  accordance  with
               the  Indenture   (whether  at  maturity  or  upon  redemption  or
               acceleration),  the First  Mortgage Bonds shall be deemed paid to
               the extent such payment or  provision  therefor has been made and
               is  considered  to be a payment of  principal  or interest on the
               Bonds.  If the Bonds or any portion  thereof  are thereby  deemed
               paid in full, First Mortgage Bonds in a principal amount equal to
               the  principal  amount of the Bonds so deemed to be paid shall be
               cancelled  and returned to the Company.  Subject to the foregoing
               or unless the  Company is  entitled  to a credit  under this Loan
               Agreement or the  Indenture,  all  payments  shall be in the full
               amount required under the First Mortgage Bonds.

                    The Issuer, by the terms of the Indenture, shall require the
               Trustee to notify in writing the Mortgage Trustee of all payments
               or credits with respect to the First Mortgage Bonds.

                    All First  Mortgage  Bonds shall equally and ratably  secure
               all outstanding Bonds."

                    "Section  5.7.   Assignment  of  Issuer's  Rights  to  First
               Mortgage  Bonds.  As security  for the payment of its Bonds,  the
               Issuer  hereby  pledges  and  assigns  to the  Trustee  the First
               Mortgage Bonds and the right to receive payments thereunder.  The
               Issuer directs the Company, and the Company agrees, to pay to the
               Trustee at its principal  corporate  trust office all payments on
               the First Mortgage  Bonds,  and other payments due and payable to
               the Trustee hereunder. The Company will make payments directly to
               the Trustee  without  defense or set-off by reason of any dispute
               between the  Company  and the  Trustee or the Issuer.  The Issuer
               hereby  agrees that the  Trustee as assignee  may enforce any and
               all rights and remedies hereunder,  but retains the right to also
               proceed in its own name  against the Company for the  enforcement
               of the  specific  performance  of any  obligation  of the Company
               under  Sections  5.2,  7.2 and  9.3;  provided,  that in any such
               action  seeking  specific  performance,  the Issuer shall have no
               rights with respect to the First Mortgage Bonds and in such event
               the  obligation  of the Company to make the payments  required to
               repay the loan hereunder and the purchase price for the Bonds and
               payments  required  under the First  Mortgage  Bonds shall remain
               unconditional as provided in Section 5.4.

                    The Issuer and the Company covenant and agree that the First
               Mortgage Bonds will at all times be (i) in fully registered (both
               principal and interest)  form; (ii) registered in the name of the
               Trustee;  (iii)  non-transferable   except  as  provided  in  the
               Mortgage;

                                      -5-

<PAGE>

               and  (iv)   appropriately   marked  to   indicate   clearly   the
               restrictions  on  the  transfer  thereof  imposed  by  this  Loan
               Agreement."

     Section  2.03.  Amendments  to Article VI of the  Original  Agreement.  (a)
Section 6.1 of the Original Agreement is hereby amended to read as follows:

                    "Section 6.1.  Maintenance of Existence.  The Company agrees
               that  during the term of this Loan  Agreement  and so long as any
               Bond is  outstanding,  it will maintain its corporate  existence,
               will continue to be a corporation in good standing under the laws
               of the State,  will not dissolve or  otherwise  dispose of all or
               substantially  all of its assets and will not consolidate with or
               merge into another legal entity or permit one or more other legal
               entities (other than one or more  subsidiaries of the Company) to
               consolidate with or merge into it, or sell or otherwise  transfer
               to another legal entity all or substantially all its assets as an
               entirety and  dissolve,  unless the  Company's  actions  shall be
               permitted  under the terms of the Insurance  Agreement and (a) in
               the case of any  merger  or  consolidation,  the  Company  is the
               surviving  corporation,  or (b)(i) the  surviving,  resulting  or
               transferee  legal entity is organized and existing under the laws
               of  the  United  States,  a  state  thereof  or the  District  of
               Columbia,  and (if not the  Company)  assumes in writing  all the
               obligations  of  the  Company  under  this  Loan  Agreement,  the
               Mortgage  and the First  Mortgage  Bonds and (ii) no event  which
               constitutes,  or which  with the giving of notice or the lapse of
               time or both  would  constitute  an Event of  Default  shall have
               occurred  and  be  continuing   immediately  after  such  merger,
               consolidation or transfer."

          (b) A new  sentence  is hereby  added to the end of Section 6.2 of the
     Original Agreement to read as follows:

               "A copy of each such  report  furnished  to the  Trustee  will be
               filed with the Bond Insurer."

          (c) The second  paragraph of Section 6.5 of the Original  Agreement is
     hereby amended to read as follows:

                    "The  Company  covenants  and agrees to notify  promptly the
               Trustee,  Issuer and the Bond  Insurer of the  occurrence  of any
               event of which the  Company  has  notice  and which  event  would
               require the Company to prepay the amounts due  hereunder  because
               of a redemption upon a determination of taxability."

          (d) Section 6.7 of the Original Agreement is hereby deleted.

                                      -6-

<PAGE>

          (e) Section 6.9 of the Original Agreement is hereby amended to read as
     follows:

               "The  Company  shall not  purchase  or  otherwise  acquire  Bonds
               without the prior written  consent of the Bond Insurer unless the
               Company  redeems  or  cancels  such  Bonds on the day of any such
               purchase."

          Section  2.04.  Amendment  to Section 8.1 of the  Original  Agreement.
     Section 8.1 of the Original Agreement is hereby amended to read as follows:

               "The  Company  may assign its rights and  obligations  under this
               Loan Agreement  with the prior written  consent of the Issuer and
               the Bond Insurer, but no assignment will relieve the Company from
               primary liability for any obligations under this Loan Agreement."

          Section 2.05. Amendments to Article IX of the Original Agreement.  (a)
     The first  paragraph  of Section 9.1 of the  Original  Agreement  is hereby
     amended to read as follows:

                    "Whenever  any  Event of  Default  under the  Indenture  has
               occurred and is continuing,  the Trustee may, with the consent of
               the Bond Insurer and shall,  upon  direction of the Bond Insurer,
               take whatever action may appear necessary or desirable to collect
               the payments then due and to become due or to enforce performance
               of any agreement of the Company in this Loan  Agreement or in the
               First Mortgage Bonds."

     (b) The last  paragraph of Section 9.1 of the Original  Agreement is hereby
amended to read as follows:

                    "Except as may  otherwise  be provided  under the  Mortgage,
               nothing in this Loan  Agreement  shall be construed to permit the
               Issuer,  the  Trustee,  any  Bondholder  or any  receiver  in any
               proceeding  brought under the Indenture to take  possession of or
               exclude the Company from  possession  of the Project by reason of
               the occurrence of an Event of Default."

     (c)  Section 9.2 of the  Original  Agreement  is hereby  amended to read as
follows:

                    "Section  9.2.  Delay  Not  Waiver;  Remedies.  A  delay  or
               omission  by the  Issuer,  the Bond  Insurer  or the  Trustee  in
               exercising any right or remedy  accruing upon an Event of Default
               shall not impair the right or remedy or constitute a waiver of or
               acquiescence  in the Event of Default.  No remedy is exclusive of
               any other remedy. All available remedies are cumulative."

                                      -7-

<PAGE>

     Section  2.06.  Amendments  to  Article X of the  Original  Agreement.  (a)
Section 10.4 of the Original Agreement is hereby amended to read as follows:

               "After the issuance of the Bonds,  this Loan Agreement may not be
               effectively  amended or terminated without the written consent of
               the  Trustee,  the  Bond  Insurer  and the  Tender  Agent  and in
               accordance with the provisions of the Indenture."

          (b)  Section  10.11 is  hereby  added to the end of  Article  X of the
     Original Agreement to read as follows:

                    "Section 10.11. Third Party Beneficiary. The Bond Insurer is
               a third party beneficiary of this Loan Agreement."


                                   ARTICLE III

                                  MISCELLANEOUS

     Section  3.01.  Agreement  Confirmed.  Except  as  amended  by  this  First
Amendment,  all of the provisions of the Original Agreement shall remain in full
force and effect,  and from and after the effective date of this First Amendment
shall be deemed to have been amended as herein set forth.

     Section 3.02. Severability.  If any provision of this First Amendment shall
be held or deemed to be or shall,  in fact, be inoperative or  unenforceable  as
applied in any particular case in any  jurisdiction or  jurisdictions  or in all
jurisdictions,  or in all cases because it conflicts with any other provision or
provisions  hereof or any  constitution or statute or rule of public policy,  or
for any other reason,  such circumstances shall not have the effect of rendering
the  provision in question  inoperative  or  unenforceable  in any other case or
circumstance, or of rendering any other provision or provisions herein contained
invalid, inoperative, or unenforceable to any extent whatever.

     Section 3.03.  Counterparts.  This First  Amendment  may be  simultaneously
executed in several counterparts,  each of which shall be an original and all of
which shall constitute but one and the same instrument.

     Section 3.04.  Applicable  Provisions of Law. This First Amendment shall be
governed by and construed in accordance with the laws of the State of Missouri.

     Section 3.05.  Effective Date. This First Amendment shall become  effective
on the date the Trustee has received the consent of the Trustee to the execution
hereof.

                                      -8-



<PAGE>




     IN WITNESS  WHEREOF,  the Issuer and the  Company  have  caused  this First
Amendment to be executed in their respective corporate names, and the Issuer has
caused its seal to be  hereunto  affixed  and  attested  by its duly  authorized
officer, all as of the date first above written.

                                         STATE ENVIRONMENTAL IMPROVEMENT AND
                                           ENERGY RESOURCES AUTHORITY


                                         By /s/ Charles D. Banks
                                           -------------------------------------
                                                        Chairman


[SEAL]

ATTEST:

By /s/ Deron L. Cherry
  --------------------------------
             Secretary

                                         UNION ELECTRIC COMPANY, DBA AMERENUE


                                         By: /s/ Jerre E. Birdsong
                                            ------------------------------------
                                         Title:  Vice President and Treasurer




                                      -9-

<PAGE>






                             CONSENT OF THE TRUSTEE

     Pursuant  to  Section  10.4  of  the  Loan  Agreement   between  the  State
Environmental  Improvement  and  Energy  Resources  Authority  of the  State  of
Missouri (the "Issuer") and Union Electric Company dba AmerenUE (the "Company"),
dated as of September 1, 1998, UMB Bank & Trust, N.A., successor to State Street
Bank and Trust  Company of Missouri,  N.A., as Trustee,  hereby  consents to the
execution  and  delivery of the First  Amendment to Loan  Agreement  dated as of
February 1, 2004 between the Issuer and the Company.


                                    UMB BANK & TRUST, N.A., successor to State
                                      Street Bank and Trust Company of Missouri,
                                      N.A.



                                    By /s/ Rebecca A. Dengler
                                      -----------------------------------------
                                      Its  Authorized Officer

Date:  February 24, 2004