A vacuum cleaner having a filter assembly 12 disposed on grill 16 between the bag chamber 7 and motor chamber 13. Bag chamber 7 has a cover 8. Filter assembly 12 has an upstanding wall 15 provided with a covering of resilient material, e.g. rubber. The cover 8 is formed with a grill 14 in a lower region. When the filter assembly is correctly installed, and the cover 8 is in position, the resilient covering of the upstanding wall 15 rests in sealing contact against the inner surface of the cover 8 and over the grill 14. If the filter assembly 12 is absent, the grill 14 provides direct fluid communication between the bag chamber 7 and the atmosphere. The cleaner will be ineffective in picking up dirt thereby alerting the user to the absence of the filter assembly.