A lubrication circuit comprising an oil tank (4) integrated into a first lubricated chamber (5) comprises an evacuation conduit (20) on a recovery conduit (10) from lubricated chambers of the circuit leading to the reservoir (4), opening up into an outlet (21) when an excessive pressure in the tank, that is a symptom of progressive filling, is reached. Application to aircraft engine lubrication circuits, particularly to guard against fuel leaks in the lubricant as a result of a defective heat exchanger.