diff --git a/CocoaPods/CocoaPods-macOS/AppDelegate.swift b/CocoaPods/CocoaPods-macOS/AppDelegate.swift
index d58030e..297ecd1 100644
--- a/CocoaPods/CocoaPods-macOS/AppDelegate.swift
+++ b/CocoaPods/CocoaPods-macOS/AppDelegate.swift
@@ -11,8 +11,6 @@ import Cocoa
 @NSApplicationMain
 class AppDelegate: NSObject, NSApplicationDelegate {
 
-
-
     func applicationDidFinishLaunching(_ aNotification: Notification) {
         // Insert code here to initialize your application
     }
@@ -21,6 +19,5 @@ class AppDelegate: NSObject, NSApplicationDelegate {
         // Insert code here to tear down your application
     }
 
-
 }
 
diff --git a/CocoaPods/CocoaPods-macOS/ViewController.swift b/CocoaPods/CocoaPods-macOS/ViewController.swift
index da2daa6..2f7d727 100644
--- a/CocoaPods/CocoaPods-macOS/ViewController.swift
+++ b/CocoaPods/CocoaPods-macOS/ViewController.swift
@@ -11,8 +11,8 @@ import EFStorage
 import KeychainAccess
 
 extension Bool: KeychainAccessStorable {
-    public func asKeychainStorable() -> KeychainAccessStorable! {
-        return "\(self)"
+    public func asKeychainAccessStorable() -> Result<AsIsKeychainAccessStorable, Error> {
+        return "\(self)".asKeychainAccessStorable()
     }
     public static func fromKeychain(_ keychain: Keychain, forKey key: String) -> Bool? {
         return String.fromKeychain(keychain, forKey: key).map {
diff --git a/CocoaPods/Cocoapods/ViewController.swift b/CocoaPods/Cocoapods/ViewController.swift
index 8c9a082..4216cb2 100644
--- a/CocoaPods/Cocoapods/ViewController.swift
+++ b/CocoaPods/Cocoapods/ViewController.swift
@@ -30,8 +30,8 @@ extension UserDefaults {
 extension UIImage: YYCacheStorable { } // Auto synthesized implmentation for NSCoding
 
 extension Double: KeychainAccessStorable {
-    public func asKeychainStorable() -> Result<AsIsKeychainAccessStorable, Error> {
-        return "\(self)".asKeychainStorable()
+    public func asKeychainAccessStorable() -> Result<AsIsKeychainAccessStorable, Error> {
+        return "\(self)".asKeychainAccessStorable()
     }
     public static func fromKeychain(_ keychain: Keychain, forKey key: String) -> Double? {
         return String.fromKeychain(keychain, forKey: key).flatMap(Double.init)
@@ -47,9 +47,14 @@ extension EFStorageKeychainAccessRef {
 
 // MARK: Allow optional default value
 
+extension Optional: AsIsUserDefaultsStorable where Wrapped: AsIsUserDefaultsStorable { }
+
 extension Optional: UserDefaultsStorable where Wrapped: UserDefaultsStorable {
-    public func asUserDefaultsStorable() -> AsIsUserDefaultsStorable! {
-        return self.flatMap { $0.asUserDefaultsStorable() }
+    public func asUserDefaultsStorable() -> Result<AsIsUserDefaultsStorable, Error> {
+        return map { $0.asUserDefaultsStorable() }
+            ?? .success(nil as Optional<Int>)
+        //                              ^
+        // It can be any type `Optional<T> where T: AsIsUserDefaultsStorable`
     }
     
     public static func fromUserDefaults(_ userDefaults: UserDefaults, forKey key: String) -> Optional<Wrapped>? {
diff --git a/Tests/EFStorageTests/EFStorageTests.swift b/Tests/EFStorageTests/EFStorageTests.swift
index 3e2bc9f..ada2c73 100644
--- a/Tests/EFStorageTests/EFStorageTests.swift
+++ b/Tests/EFStorageTests/EFStorageTests.swift
@@ -9,8 +9,8 @@ import XCTest
 import KeychainAccess
 
 extension Bool: KeychainAccessStorable {
-    public func asKeychainStorable() -> Result<AsIsKeychainAccessStorable, Error> {
-        return "\(self)".asKeychainStorable()
+    public func asKeychainAccessStorable() -> Result<AsIsKeychainAccessStorable, Error> {
+        return "\(self)".asKeychainAccessStorable()
     }
     public static func fromKeychain(_ keychain: Keychain, forKey key: String) -> Bool? {
         guard let string = try? keychain.getString(key) else { return nil }