diff --git a/CovidSafe/Herald/Sensor/BLE/BLEDatabase.swift b/CovidSafe/Herald/Sensor/BLE/BLEDatabase.swift
index 63ebc11..fb65b4f 100644
--- a/CovidSafe/Herald/Sensor/BLE/BLEDatabase.swift
+++ b/CovidSafe/Herald/Sensor/BLE/BLEDatabase.swift
@@ -164,18 +164,24 @@ public class BLEDevice : NSObject {
     /// Service characteristic for signalling between BLE devices, e.g. to keep awake
     var signalCharacteristic: CBCharacteristic? {
         didSet {
-            lastUpdatedAt = Date()
+            if signalCharacteristic != nil {
+                lastUpdatedAt = Date()
+            }
             delegate.device(self, didUpdate: .signalCharacteristic)
         }}
     /// Service characteristic for reading payload data
     var payloadCharacteristic: CBCharacteristic? {
         didSet {
-            lastUpdatedAt = Date()
+            if payloadCharacteristic != nil {
+                lastUpdatedAt = Date()
+            }
             delegate.device(self, didUpdate: .payloadCharacteristic)
         }}
     var legacyPayloadCharacteristic: CBCharacteristic? {
         didSet {
-            lastUpdatedAt = Date()
+            if legacyPayloadCharacteristic != nil {
+                lastUpdatedAt = Date()
+            }
             delegate.device(self, didUpdate: .payloadCharacteristic)
         }}
     /// Device operating system, this is necessary for selecting different interaction procedures for each platform.