Opinion by

Set-off may only be allowed when the party claiming it has a cause of action upon which suit may at once be instituted: Pennell v. Grubb, 13 Pa. 552. Complaint is made of the charge of the court wherein the trial judge stated that the value of the two cows lost could not be set off against the plaintiff’s claim. The contract of hire specified that in case of the loss or death of any cow during the period of hire it should be replaced with one of the same value and age at the lessee’s expense. It did not specify the time when such cows were to be replaced. If it were not reasonably within the defendant’s means to immediately or for sometime after the loss or death to replace the cows, the contract did not authorize a forfeiture on that ground. The plaintiff, by complying with all the terms of the contract and paying the consideration stipulated in the lease for the hiring of the cattle, would become the owner of all the cattle held under the lease. This condition would continue to be operative until the contract was completed. The plaintiff had submitted evidence showing that he had been re*428lieved from the obligation of replacing the cows, and that, if there was a forfeiture for failure to replace when demanded, it had been waived. Forfeitures should not be sustained unless it clearly appears from the contract that such was the intention, or the facts are such that justify the exercise of this right. The court submitted the question to the jury. After carefully reviewing the testimony and the charge of the court as a whole, wé do not think reversible error was committed.

The judgment is affirmed.