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                                                                    EXHIBIT 3.4

                            CERTIFICATE OF CORRECTION
                                     TO THE
                      RESTATED CERTIFICATE OF INCORPORATION
                                       OF
                                   DYAX CORP.
                  FILED IN THE OFFICE OF THE SECRETARY OF STATE
                         OF DELAWARE ON AUGUST 18, 2000

         Pursuant to Section 103(f) of the Delaware General Corporation Law (the
"DGCL"), Dyax Corp., a Delaware corporation (the "Corporation") hereby certifies
as follows:

         1. That a Restated Certificate of Incorporation of the Corporation (the
            "Certificate") was filed with the Secretary of State of Delaware on
            August 18, 2000 and that said Certificate requires correction as
            permitted by Section 103(f) of the DGCL.

         2. The inaccuracy or defect to be corrected in said Certificate is as
            follows: Section 2 of ARTICLE FIFTH of the said Certificate
            mistakenly describes the dates of expiration of the three classes of
            directors referred to therein as 1999, 2000 and 2001, respectively.

         3. Section (2) of ARTICLE FIFTH of the Certificate is hereby corrected
            to read in its entirety as follows:

               "2. The directors shall be divided into three classes, as nearly
                   equal in number as the then total number of directors
                   constituting the entire Board permits, with the term of
                   office of one class expiring each year. The initial Class I
                   directors elected by the stockholders of the Corporation
                   shall hold office for a term expiring at the 2001 annual
                   meeting of stockholders; the initial Class II directors
                   elected by the stockholders of the Corporation shall hold
                   office for a term expiring at the 2002 annual meeting of
                   stockholders; and the initial Class III directors elected by
                   the stockholders of the Corporation shall hold office for a
                   term expiring at the 2003 annual meeting of stockholders. At
                   each such annual meeting of stockholders and at each annual
                   meeting thereafter, successors to the class of directors
                   whose term expires at that meeting shall be elected for a
                   term expiring at the third annual meeting following their
                   election and until their successors shall be elected and
                   qualified, subject to prior death, resignation, retirement or
                   removal. If the number of directors is changed, any increase
                   or decrease shall be apportioned among the classes so as to
                   maintain the number of directors in each class as nearly
                   equal as possible, but in no event will a decrease in the
                   number of directors shorten the term of any incumbent
                   director. Notwithstanding the foregoing, and except as
                   otherwise required by law, whenever the holders of any one or
                   more series of Preferred Stock shall have the right, voting
                   separately as a class, to elect one or more directors of the
                   Corporation, the election, terms of office and other features
                   of such directorships shall be governed by the terms of the
                   vote establishing such series, and such

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                   directors so elected shall not be divided into classes
                   pursuant to this Article FIFTH unless expressly provided by
                   such terms."

IN WITNESS WHEREOF, the Corporation has caused this Certificate of Correction to
be signed by its Secretary this 22nd day of April 2002.

                                              DYAX CORP.

                                              By: /s/ Nathaniel S. Gardiner
                                                  -----------------------------
                                                  Nathaniel S. Gardiner
                                                  Secretary