Leitz REDYX Fuse

I have an old Leitz REDYX variable AC transformer for 6V tungsten microscopy lamps. Unfortunatly it does not contain a fuse. So I added a small european standard 5x20mm 500mA (slow, ceramic w/ extinguisher) fuse on the input tap that goes to the switch. This should keep the transformer from catching fire in case it has an isolation failure.