According to one method for preserving stable calls during failover, during a dialog between two user endpoints, a determination is made whether a standby call processor has become operational, such as when a corresponding primary call processor is in fault. Responsive to determining that the standby call processor has become operational, a signaling protocol message is received from a requester. A determination is made whether the message includes an in-dialog signaling protocol request. Responsive to determining that the message includes the in-dialog request, a determination is made whether a call state associated with the dialog is found in memory. Responsive to determining that the call state associated with the dialog is not found in memory, a non-call terminating error response is made responding to the in-dialog request. The non-call terminating error response may cause the requester to terminate the in-dialog request but not terminate the dialog.