Questão jurídica principal
Whether the rent default termination under Art. 257d CO was valid despite the tenant's objections about the claimed arrears.
Decisão extraída
The termination was valid because the tenant admitted being in arrears and did not pay within the grace period; the amount claimed by the landlord need not exactly match the amount later acknowledged by the tenant.
Fundamentação extraída
A tenant in arrears is in default within Art. 257d CO. The decisive point was not the precise amount stated in the warning, but whether the tenant failed to pay within the 30-day period. The canton court's findings bound the Federal Court.