Massachusetts General Laws
Article 4 - Creation, Validity, Modification and Termination of Trust
Section 415 - Reformation to Correct Mistakes

Section 415. Reformation to correct mistakes
The court may reform the terms of a trust, even if unambiguous, to conform the terms to the settlor's intention if it is proved by clear and convincing evidence that the settlor's intent or the terms of the trust were affected by a mistake of fact or law, whether in expression or inducement.