Under Section 87, a material alteration of a negotiable instrument without consent renders the instrument what?

Section 87 of the Negotiable Instruments Act provides that any material alteration of a negotiable instrument renders it void as against anyone who is a party thereto at the time of making such alteration and does not consent to it. A material alteration is one that changes the rights, liabilities or legal effect of the instrument. The provision protects parties from unauthorised changes. However, an alteration made to carry out the common intention may be permissible.