diff --git a/Source/CentralManagerRestoredState.swift b/Source/CentralManagerRestoredState.swift
index 81d6e62c..7e40adb4 100644
--- a/Source/CentralManagerRestoredState.swift
+++ b/Source/CentralManagerRestoredState.swift
@@ -60,7 +60,12 @@ public struct CentralManagerRestoredState: CentralManagerRestoredStateType {
         let cbServices = arrayOfAnyObjects.flatMap { $0 as? CBService }
         #endif
 
-        return cbServices.map { Service(peripheral: centralManager.retrievePeripheral(for: $0.peripheral),
+        return cbServices.compactMap {
+            guard let peripheral = $0.peripheral else {
+                return nil
+            }
+            
+            return Service(peripheral: centralManager.retrievePeripheral(for: peripheral),
                                         service: $0) }
     }
 }
diff --git a/Source/Characteristic.swift b/Source/Characteristic.swift
index f4f2edec..e7e726dd 100644
--- a/Source/Characteristic.swift
+++ b/Source/Characteristic.swift
@@ -40,8 +40,11 @@ public class Characteristic {
         self.service = service
     }
 
-    convenience init(characteristic: CBCharacteristic, peripheral: Peripheral) {
-        let service = Service(peripheral: peripheral, service: characteristic.service)
+    convenience init?(characteristic: CBCharacteristic, peripheral: Peripheral) {
+        guard let bluetoothService = characteristic.service else {
+            return nil
+        }
+        let service = Service(peripheral: peripheral, service: bluetoothService)
         self.init(characteristic: characteristic, service: service)
     }
 
diff --git a/Source/Descriptor.swift b/Source/Descriptor.swift
index dff8f3f3..472b3020 100644
--- a/Source/Descriptor.swift
+++ b/Source/Descriptor.swift
@@ -28,9 +28,14 @@ public class Descriptor {
         self.characteristic = characteristic
     }
 
-    convenience init(descriptor: CBDescriptor, peripheral: Peripheral) {
-        let service = Service(peripheral: peripheral, service: descriptor.characteristic.service)
-        let characteristic = Characteristic(characteristic: descriptor.characteristic, service: service)
+    convenience init?(descriptor: CBDescriptor, peripheral: Peripheral) {
+        guard let bluetoothService = descriptor.characteristic?.service,
+        let bluetoothCharacteristic = descriptor.characteristic else {
+          return nil
+        }
+            let service = Service(peripheral: peripheral, service: bluetoothService)
+            let characteristic = Characteristic(characteristic: bluetoothCharacteristic,
+                                                service: service)
         self.init(descriptor: descriptor, characteristic: characteristic)
     }
 
diff --git a/Source/Peripheral.swift b/Source/Peripheral.swift
index 9a783c74..4a2c8319 100644
--- a/Source/Peripheral.swift
+++ b/Source/Peripheral.swift
@@ -403,6 +403,10 @@ public class Peripheral {
             .map { [weak self] (cbCharacteristic, error) -> Characteristic in
                 guard let strongSelf = self else { throw BluetoothError.destroyed }
                 let characteristic = characteristic ?? Characteristic(characteristic: cbCharacteristic, peripheral: strongSelf)
+                guard let characteristic = characteristic else {
+                    throw BluetoothError.unknownWriteType
+                }
+
                 if let error = error {
                     throw BluetoothError.characteristicWriteFailed(characteristic, error)
                 }
@@ -499,6 +503,9 @@ public class Peripheral {
             .map { [weak self] (cbCharacteristic, error) -> Characteristic in
                 guard let strongSelf = self else { throw BluetoothError.destroyed }
                 let characteristic = characteristic ?? Characteristic(characteristic: cbCharacteristic, peripheral: strongSelf)
+                guard let characteristic = characteristic else {
+                    throw BluetoothError.unknownWriteType
+                }
                 if let error = error {
                     throw BluetoothError.characteristicReadFailed(characteristic, error)
                 }
@@ -569,6 +576,9 @@ public class Peripheral {
             .map { [weak self] (cbCharacteristic, error) -> Characteristic in
                 guard let strongSelf = self else { throw BluetoothError.destroyed }
                 let characteristic = Characteristic(characteristic: cbCharacteristic, peripheral: strongSelf)
+                guard let characteristic = characteristic else {
+                    throw BluetoothError.unknownWriteType
+                }
                 if let error = error {
                     throw BluetoothError.characteristicSetNotifyValueFailed(characteristic, error)
                 }
@@ -638,6 +648,9 @@ public class Peripheral {
             .map { [weak self] (cbDescriptor, error) -> Descriptor in
                 guard let strongSelf = self else { throw BluetoothError.destroyed }
                 let descriptor = descriptor ?? Descriptor(descriptor: cbDescriptor, peripheral: strongSelf)
+                guard let descriptor = descriptor else {
+                    throw BluetoothError.unknownWriteType
+                }
                 if let error = error {
                     throw BluetoothError.descriptorWriteFailed(descriptor, error)
                 }
@@ -667,6 +680,9 @@ public class Peripheral {
             .map { [weak self] (cbDescriptor, error) -> Descriptor in
                 guard let strongSelf = self else { throw BluetoothError.destroyed }
                 let descriptor = descriptor ?? Descriptor(descriptor: cbDescriptor, peripheral: strongSelf)
+                guard let descriptor = descriptor else {
+                    throw BluetoothError.unknownWriteType
+                }
                 if let error = error {
                     throw BluetoothError.descriptorReadFailed(descriptor, error)
                 }