Exhibit NO. 99.(a) 12

MASSACHUSETTS INVESTORS GROWTH STOCK FUND

CERTIFICATION OF AMENDMENT

TO THE DECLARATION OF TRUST

TERMINATION OF CLASSES

Pursuant to Section 9.2(b) of the Amended and Restated Declaration of Trust, dated as of December 16, 2004, as amended (the “Declaration”), of Massachusetts Investors Growth Stock Fund, a business trust organized under the laws of The Commonwealth of Massachusetts (the “Trust”), the undersigned, constituting a majority of the Trustees of the Trust, do hereby certify that Class 529A Shares, Class 529B Shares, and Class 529C Shares of the Trust have been terminated effective upon the filing of this instrument with the Secretary of State of The Commonwealth of Massachusetts.

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 June 9, 2022 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.

Steven E. Buller	Robert J. Manning
Steven E. Buller	Robert J. Manning
c/o MFS Investment Management	MFS Investment Management
111 Huntington Avenue	111 Huntington Avenue
Boston, MA 02199	Boston, MA 02199
John A. Caroselli	Clarence Otis, Jr.
John A. Caroselli	Clarence Otis, Jr.
c/o MFS Investment Management	MFS Investment Management
111 Huntington Avenue	111 Huntington Avenue
Boston, MA 02199	Boston, MA 02199
Maureen R. Goldfarb	Michael W. Roberge
Maureen R. Goldfarb	Michael W. Roberge
c/o MFS Investment Management	c/o MFS Investment Management
111 Huntington Avenue	111 Huntington Avenue
Boston, MA 02199	Boston, MA 02199
Peter D. Jones	Maryanne L. Roepke
Peter D. Jones	Maryanne L. Roepke
c/o MFS Investment Management	MFS Investment Management
111 Huntington Avenue	111 Huntington Avenue
Boston, MA 02199	Boston, MA 02199
John P. Kavanaugh	Laurie J. Thomsen
John P. Kavanaugh	Laurie J. Thomsen
c/o MFS Investment Management	c/o MFS Investment Management
111 Huntington Avenue	111 Huntington Avenue
Boston, MA 02199	Boston, MA 02199
James W. Kilman, Jr.
James W. Kilman, Jr.
c/o MFS Investment Management
111 Huntington Avenue
Boston, MA 02199