EXHIBIT NO. 99.(a)17

MFS SERIES TRUST X

MFS STRATEGIC VALUE FUND

Pursuant to Section 9.2(b) of the Amended and Restated Declaration of Trust, dated December 16, 2004, as amended, (the “Declaration”), of MFS Series Trust X (the “Trust”), the undersigned, constituting a majority of the Trustees of the Trust, do hereby certify that MFS Strategic Value Fund, a series of the Trust, has been terminated.

IN WITNESS WHEREOF, a majority of the Trustees of the Trust have executed this amendment, in one or more counterparts, all constituting a single instrument, as an instrument under seal in The Commonwealth of Massachusetts, as of July 31, 2009 and further certify, as provided by the provisions of Section 9.3(c) of the Declaration, that this amendment was duly adopted by the undersigned in accordance with Section 9.3(a) of the Declaration.

ROBERT E. BUTLER

Robert E. Butler

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

LAWRENCE H. COHN

Lawrence H. Cohn

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

MAUREEN R. GOLDFARB

Maureen R. Goldfarb

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

DAVID H. GUNNING

David H. Gunning

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

WILLIAM R. GUTOW

William R. Gutow

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

MICHAEL HEGARTY

Michael Hegarty

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

J. ATWOOD IVES

J. Atwood Ives

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

JOHN P. KAVANAUGH

John P. Kavanaugh

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

ROBERT J. MANNING

Robert J. Manning

MFS Investment Management

500 Boylston Street

Boston, MA 02116

ROBERT C. POZEN

Robert C. Pozen

MFS Investment Management

500 Boylston Street

Boston, MA 02116

J. DALE SHERRATT

J. Dale Sherratt

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

LAURIE J. THOMSEN

Laurie J. Thomsen

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116

ROBERT W. UEK

Robert W. Uek

c/o MFS Investment Management

500 Boylston Street

Boston, MA 02116