diff --git a/Sources/SwiftySensors/CoreBluetooth.swift b/Sources/SwiftySensors/CoreBluetooth.swift
index 810801f..2469c9a 100755
--- a/Sources/SwiftySensors/CoreBluetooth.swift
+++ b/Sources/SwiftySensors/CoreBluetooth.swift
@@ -17,12 +17,12 @@ extension CBCharacteristic {
      - parameter enabled: Notification Flag
      */
     public func notify(_ enabled: Bool) {
-        service.peripheral.setNotifyValue(enabled, for: self)
+        service?.peripheral?.setNotifyValue(enabled, for: self)
     }
     
     /// Read the value of the Characteristic
     public func read() {
-        service.peripheral.readValue(for: self)
+        service?.peripheral?.readValue(for: self)
     }
     
     /**
diff --git a/Sources/SwiftySensors/Sensor.swift b/Sources/SwiftySensors/Sensor.swift
index 0cdac60..50784aa 100755
--- a/Sources/SwiftySensors/Sensor.swift
+++ b/Sources/SwiftySensors/Sensor.swift
@@ -275,7 +275,7 @@ extension Sensor: CBPeripheralDelegate {
     
     /// :nodoc:
     public func peripheral(_ peripheral: CBPeripheral, didUpdateValueFor characteristic: CBCharacteristic, error: Error?) {
-        guard let service = services[characteristic.service.uuid.uuidString] else { return }
+        guard let service = services[characteristic.service?.uuid.uuidString ?? ""] else { return }
         guard let char = service.characteristics[characteristic.uuid.uuidString] else { return }
         if char.cbCharacteristic !== characteristic {
             char.cbCharacteristic = characteristic
@@ -286,7 +286,7 @@ extension Sensor: CBPeripheralDelegate {
     
     /// :nodoc:
     public func peripheral(_ peripheral: CBPeripheral, didWriteValueFor characteristic: CBCharacteristic, error: Error?) {
-        guard let service = services[characteristic.service.uuid.uuidString] else { return }
+        guard let service = services[characteristic.service?.uuid.uuidString ?? ""] else { return }
         guard let char = service.characteristics[characteristic.uuid.uuidString] else { return }
         if char.cbCharacteristic !== characteristic {
             char.cbCharacteristic = characteristic