An exception, in form at least, to the rule that the new promise must be identical in its terms with the original obligation exists in case of a promise subsequently to sign a guaranty of another's debt. Such a promise is within the statute, for it is regarded as the equivalent of undertaking an immediate obligation of guaranty.51a Therefore a promise to a creditor to sign negotiable paper for the accommodation of his debtor either as an indorser,51b maker,51c or acceptor,52 must be in writing. It will be noticed that these promises are not only absolute in form, but that the obligation incurred by signing the instrument is not conditional on the liability of the principal debtor. The indorser of a note is not excused from liability because the maker has a defence or lacks capacity, if value was given for the indorsement.

A promise to the creditor to discount bis debtor's commercial paper without recourse is similar in effect and must also be in writing.53