Minn. Stat. § 513.09

Every conveyance or charge of or upon any estate or interest in lands, containing any provision for the revocation, determination, or alteration of such estate or interest, or of any part thereof, at the will of the grantor, shall be void, as against subsequent purchasers from such grantor for a valuable consideration, of any estate or interest liable to be so revoked or determined, although the same is not expressly revoked, determined, or altered by such grantor, by virtue of the power reserved or expressed in such prior conveyance or charge.