<PAGE>

                                                                    EXHIBIT 4.40

                          SUPPLEMENTAL INDENTURE NO. 2

                        (ALLFIRST PREFERRED ASSET TRUST)

         SUPPLEMENTAL INDENTURE NO. 2, dated as of April 1, 2003 (this "Second
Supplemental Indenture"), by and between M&T Bank Corporation, a New York
corporation (the "Company") and successor by merger to Allfirst Financial Inc.
("Allfirst"), having its principal executive office at One M&T Plaza, Buffalo,
New York 14203, and The Bank of New York, a New York banking corporation, as
trustee (the "Trustee").

                                    RECITALS

         1.       The Trustee is the trustee under that certain Indenture, dated
as of July 13, 1999, as supplemented by Supplemental Indenture No. 1 dated
September 15, 1999 (as supplemented, the "Indenture"), between the Trustee and
Allfirst. Under the Indenture, Allfirst issued $105,310,000 aggregate principal
amount of Floating Rate Junior Subordinated Debentures due July 15, 2029 (the
"Outstanding Junior Subordinated Securities").

         2.       As of the date hereof, Allfirst, a Delaware corporation,
merged with and into the Company, with the Company being the surviving
corporation, whereupon the separate corporate existence of Allfirst has ceased.

         3.       The Company now wishes, pursuant to Section 801 of the
Indenture, expressly to assume all of Allfirst's obligations under the Indenture
and the Outstanding Junior Subordinated Securities.

         NOW, THEREFORE, in consideration of the premises, the agreements
contained herein and other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto agree as
follows:

         1.       Certain Definitions; Interpretation; Recitals. A capitalized
term used in this Second Supplemental Indenture (including the above Recitals)
without definition and defined in the Indenture shall have the meaning given it
in the Indenture. All references in the Indenture to "this Indenture" or words
of similar import, and the terms "hereby", "hereof", "hereunder", "herein" and
any similar terms, as used in the Indenture, shall be deemed to refer to the
Indenture as supplemented by this Second Supplemental Indenture. The above
Recitals are an integral part of this Second Supplemental Indenture.

         2.       Assumption. Pursuant to Section 801 of the Indenture, the
Company hereby expressly assumes the due and punctual payment of the principal
of, premium, if any, and interest (including any additional interest) on all the
Debentures (which consist of the Outstanding Junior Subordinated Securities) and
the due and punctual performance and observance of every covenant and condition
of the Indenture on the part of Allfirst to be performed or observed, as fully
and completely as if the Company had originally executed and delivered the
Indenture to the Trustee

<PAGE>

and had issued the Outstanding Junior Subordinated Securities. The Company
hereby succeeds to and is substituted for Allfirst with the same effect as if it
had been named in the Indenture as the party of the first part.

         3.       Amendments. From and after the date of this Second
Supplemental Indenture, all references in the Indenture and in the Outstanding
Junior Subordinated Securities to "First Maryland Bancorp," "Allfirst Financial
Inc." or "the Company" shall be references to M&T Bank Corporation, a New York
corporation and the successor by merger to Allfirst.

         4.       Representations, Warranties, Etc. The Company represents and
warrants to and covenants with the Trustee as follows:

         (a)      The Company is a corporation duly formed, validly existing and
in good standing under the laws of the State of New York, with the power and
authority to own its assets and conduct its business as currently conducted, to
enter into this Second Supplemental Indenture and to perform its obligations
under the Indenture and the Outstanding Junior Subordinated Securities.

         (b)      Allfirst has been duly and validly merged into the Company,
and the Company has succeeded to all of the rights, privileges, duties and
responsibilities of Allfirst, under the laws of the States of New York and
Delaware.

         (c)      The execution, delivery and performance of this Second
Supplemental Indenture have been duly authorized by all necessary action on the
part of the Company, and this Second Supplemental Indenture represents the valid
and binding obligation of the Company, enforceable against the Company in
accordance with its terms.

         (d)      No Event of Default, and no event which with notice or lapse
of time or both would constitute an event of Default, has happened and is
continuing as a result of the merger of Allfirst into the Company or otherwise.

         5.       Other Agreements. (a) Except as expressly supplemented or
amended hereby, all of the terms, provisions and conditions of the Indenture and
the Outstanding Junior Subordinated Securities and all documents executed in
connection therewith are ratified and confirmed and shall remain in full force
and effect and shall remain enforceable and binding in accordance with their
terms. This Second Supplemental Indenture shall in no way operate as a novation,
release or discharge of any of the obligations the Company under, or of any of
the provisions of, the Indenture and the Outstanding Junior Subordinated
Securities.

         (b)      This Second Supplemental Indenture does not, and shall not be
deemed to, constitute a waiver of any past, present or future defaults by the
Company under the Indenture or the Outstanding Junior Subordinated Securities,
and the Trustee expressly reserves all rights and remedies available to it under
the Indenture, the Outstanding Junior Subordinated Securities and under
applicable law for the benefit of Holders from time to time.

                                       2

<PAGE>

         (c)      This Second Supplemental Indenture shall be governed by and
construed in accordance with the laws of the State of New York.

         (d)      Provided that each party executes a copy hereof, this Second
Supplemental Indenture may be executed in two or more counterparts, each of
which shall be deemed an original but all of which when taken together shall
constitute one and the same agreement.

         (e)      In the event of a conflict between the terms and conditions of
the Indenture and the terms and conditions of this Second Supplemental
Indenture, then the terms and conditions of this Second Supplemental Indenture
shall prevail.

         (f)      The statements herein are deemed to be those of the Company
and not those of the Trustee. The Trustee makes no representation as to the
validity or sufficiency of this Second Supplemental Indenture.

         IN WITNESS WHEREOF, the parties hereto have caused this Second
Supplemental Indenture to be duly executed as of the date first written above.

                                M&T BANK CORPORATION

                                By:     /s/ Michael S. Piemonte
                                    -------------------------------------
                                      Name: Michael S. Piemonte
                                      Title: Senior Vice President

                                By:     /s/ Brian R. Yoshida
                                    --------------------------------------
                                     Name: Brian R. Yoshida
                                     Title: Assistant Secretary

                                THE BANK OF NEW YORK

                                By:     /s/ Geovanni Barris
                                    ---------------------------------------
                                     Name: Geovanni Barris
                                     Title: Vice President

                                       3