Illinois Surety Co. v. Peeler (1939 Statutory Interpret)

When Peeler sought to enforce the surety bond following the principal's default, the court held that Illinois Surety Company's liability was strictly limited to the scope of its written undertaking—no more, no less. The case established that any material modification to the underlying principal obligation without the surety's explicit consent operates as a discharge of the surety's liability, protecting the surety from exposure beyond what it had contractually assumed. This principle protects surety companies from creditors unilaterally expanding their obligations through side agreements or changes to the principal's contract, ensuring the surety's liability remains co-extensive with its original bond commitment.