diff --git a/Sources/EFStorageKeychainAccess/EFStorage+KeychainAccess.swift b/Sources/EFStorageKeychainAccess/EFStorage+KeychainAccess.swift
index d02a675..9ea6396 100644
--- a/Sources/EFStorageKeychainAccess/EFStorage+KeychainAccess.swift
+++ b/Sources/EFStorageKeychainAccess/EFStorage+KeychainAccess.swift
@@ -34,7 +34,7 @@ public enum AsIsKeychainAccessStorable {
 }
 
 public protocol KeychainAccessStorable {
-    func asKeychainStorable() -> Result<AsIsKeychainAccessStorable, Error>
+    func asKeychainAccessStorable() -> Result<AsIsKeychainAccessStorable, Error>
     static func fromKeychain(_ keychain: Keychain, forKey key: String) -> Self?
 }
 
@@ -60,7 +60,7 @@ public class EFStorageKeychainAccessRef<Content: KeychainAccessStorable>: EFSing
                 try? storage.remove(key)
                 return
             }
-            switch newValue.asKeychainStorable() {
+            switch newValue.asKeychainAccessStorable() {
             case .success(.string(let string)):
                 do {
                     try storage.set(string, key: key)
diff --git a/Sources/EFStorageKeychainAccess/KeychainAccess+NSCoding.swift b/Sources/EFStorageKeychainAccess/KeychainAccess+NSCoding.swift
index f7d74ce..ba2318d 100644
--- a/Sources/EFStorageKeychainAccess/KeychainAccess+NSCoding.swift
+++ b/Sources/EFStorageKeychainAccess/KeychainAccess+NSCoding.swift
@@ -9,7 +9,7 @@ import KeychainAccess
 import Foundation
 
 public extension KeychainAccessStorable where Self: NSCoding {
-    func asKeychainStorable() -> Result<AsIsKeychainAccessStorable, Error> {
+    func asKeychainAccessStorable() -> Result<AsIsKeychainAccessStorable, Error> {
         return .success(.data(NSKeyedArchiver.archivedData(withRootObject: self)))
     }
     static func fromKeychain(_ keychain: Keychain, forKey key: String) -> Self? {
diff --git a/Sources/EFStorageKeychainAccess/KeychainAccess+Primitives.swift b/Sources/EFStorageKeychainAccess/KeychainAccess+Primitives.swift
index c71bfea..c20f8e2 100644
--- a/Sources/EFStorageKeychainAccess/KeychainAccess+Primitives.swift
+++ b/Sources/EFStorageKeychainAccess/KeychainAccess+Primitives.swift
@@ -9,7 +9,7 @@ import KeychainAccess
 import Foundation
 
 extension String: KeychainAccessStorable {
-    public func asKeychainStorable() -> Result<AsIsKeychainAccessStorable, Error> {
+    public func asKeychainAccessStorable() -> Result<AsIsKeychainAccessStorable, Error> {
         return .success(.string(self))
     }
     public static func fromKeychain(_ keychain: Keychain, forKey key: String) -> Self? {
@@ -18,7 +18,7 @@ extension String: KeychainAccessStorable {
 }
 
 extension Data: KeychainAccessStorable {
-    public func asKeychainStorable() -> Result<AsIsKeychainAccessStorable, Error> {
+    public func asKeychainAccessStorable() -> Result<AsIsKeychainAccessStorable, Error> {
         return .success(.data(self))
     }
     public static func fromKeychain(_ keychain: Keychain, forKey key: String) -> Self? {
diff --git a/Sources/EFStorageKeychainAccess/KeychainAccess+RawRepresentable.swift b/Sources/EFStorageKeychainAccess/KeychainAccess+RawRepresentable.swift
index 3d0c490..eebb676 100644
--- a/Sources/EFStorageKeychainAccess/KeychainAccess+RawRepresentable.swift
+++ b/Sources/EFStorageKeychainAccess/KeychainAccess+RawRepresentable.swift
@@ -8,8 +8,8 @@
 import KeychainAccess
 
 public extension KeychainAccessStorable where Self: RawRepresentable, Self.RawValue: KeychainAccessStorable {
-    func asKeychainStorable() -> Result<AsIsKeychainAccessStorable, Error> {
-        return rawValue.asKeychainStorable()
+    func asKeychainAccessStorable() -> Result<AsIsKeychainAccessStorable, Error> {
+        return rawValue.asKeychainAccessStorable()
     }
     static func fromKeychain(_ keychain: Keychain, forKey key: String) -> Self? {
         return RawValue.fromKeychain(keychain, forKey: key)
diff --git a/Sources/EFStorageUserDefaults/EFStorage+UserDefaults.swift b/Sources/EFStorageUserDefaults/EFStorage+UserDefaults.swift
index eeb5d5f..bb4e7ae 100644
--- a/Sources/EFStorageUserDefaults/EFStorage+UserDefaults.swift
+++ b/Sources/EFStorageUserDefaults/EFStorage+UserDefaults.swift
@@ -18,7 +18,7 @@ extension UserDefaults: EFUnderlyingStorage {
 
 /// NSData, NSString, NSNumber, NSDate, NSArray, or NSDictionary
 public protocol UserDefaultsStorable {
-    func asUserDefaultsStorable() -> AsIsUserDefaultsStorable!
+    func asUserDefaultsStorable() -> Result<AsIsUserDefaultsStorable, Error>
     static func fromUserDefaults(_ userDefaults: UserDefaults, forKey key: String) -> Self?
 }
 
@@ -43,18 +43,19 @@ public class EFStorageUserDefaultsRef<Content: UserDefaultsStorable>: EFSingleIn
             guard let newValue = content else {
                 return storage.removeObject(forKey: key)
             }
-            if let storable = newValue.asUserDefaultsStorable()  {
+            switch newValue.asUserDefaultsStorable() {
+            case .success(let storable):
                 storage.set(storable, forKey: key)
-            } else {
-                onConversionFailure(for: newValue)
+            case .failure(let error):
+                onConversionFailure(for: newValue, dueTo: error)
             }
         }
     }
     
-    public dynamic func onConversionFailure(for content: Content) {
+    public dynamic func onConversionFailure(for content: Content, dueTo error: Error) {
         assertionFailure("""
         \(content) of type \(type(of: content)) \
-        is not storable in user defaults.
+        is not storable in user defaults because \(error).
         """)
     }
     
diff --git a/Sources/EFStorageUserDefaults/UserDefaults+Codable.swift b/Sources/EFStorageUserDefaults/UserDefaults+Codable.swift
index 071a101..060b485 100644
--- a/Sources/EFStorageUserDefaults/UserDefaults+Codable.swift
+++ b/Sources/EFStorageUserDefaults/UserDefaults+Codable.swift
@@ -8,17 +8,8 @@
 import Foundation
 
 public extension UserDefaultsStorable where Self: Codable {
-    func asUserDefaultsStorable() -> UserDefaultsStorable! {
-        do {
-            return try JSONEncoder().encode(self)
-        } catch {
-            return onConversionFailure(dueTo: error)
-        }
-    }
-    
-    dynamic func onConversionFailure(dueTo error: Error) -> UserDefaultsStorable! {
-        assertionFailure(error.localizedDescription)
-        return nil
+    func asUserDefaultsStorable() -> Result<AsIsUserDefaultsStorable, Error> {
+        return Result { try JSONEncoder().encode(self) }
     }
     
     static func fromUserDefaults(_ userDefaults: UserDefaults, forKey key: String) -> Self? {
diff --git a/Sources/EFStorageUserDefaults/UserDefaults+NSCoding.swift b/Sources/EFStorageUserDefaults/UserDefaults+NSCoding.swift
index 06f671e..5e660f8 100644
--- a/Sources/EFStorageUserDefaults/UserDefaults+NSCoding.swift
+++ b/Sources/EFStorageUserDefaults/UserDefaults+NSCoding.swift
@@ -8,8 +8,8 @@
 import Foundation
 
 public extension UserDefaultsStorable where Self: NSCoding {
-    func asUserDefaultsStorable() -> AsIsUserDefaultsStorable! {
-        return NSKeyedArchiver.archivedData(withRootObject: self)
+    func asUserDefaultsStorable() -> Result<AsIsUserDefaultsStorable, Error> {
+        return NSKeyedArchiver.archivedData(withRootObject: self).asUserDefaultsStorable()
     }
     static func fromUserDefaults(_ userDefaults: UserDefaults, forKey key: String) -> Self? {
         guard let data = userDefaults.data(forKey: key) else { return nil }
diff --git a/Sources/EFStorageUserDefaults/UserDefaults+Primitives.swift b/Sources/EFStorageUserDefaults/UserDefaults+Primitives.swift
index d573979..ee6dd63 100644
--- a/Sources/EFStorageUserDefaults/UserDefaults+Primitives.swift
+++ b/Sources/EFStorageUserDefaults/UserDefaults+Primitives.swift
@@ -8,8 +8,8 @@
 import Foundation
 
 extension URL: UserDefaultsStorable {
-    public func asUserDefaultsStorable() -> AsIsUserDefaultsStorable! {
-        return absoluteString
+    public func asUserDefaultsStorable() -> Result<AsIsUserDefaultsStorable, Error> {
+        return absoluteString.asUserDefaultsStorable()
     }
     public static func fromUserDefaults(_ userDefaults: UserDefaults, forKey key: String) -> URL? {
         return userDefaults.url(forKey: key)
@@ -20,8 +20,8 @@ extension URL: UserDefaultsStorable {
 public protocol AsIsUserDefaultsStorable: UserDefaultsStorable { }
 
 extension AsIsUserDefaultsStorable {
-    public func asUserDefaultsStorable() -> AsIsUserDefaultsStorable! {
-        return self
+    public func asUserDefaultsStorable() -> Result<AsIsUserDefaultsStorable, Error> {
+        return .success(self)
     }
     public static func fromUserDefaults(_ userDefaults: UserDefaults, forKey key: String) -> Self? {
         guard let object = userDefaults.object(forKey: key) else { return nil }
diff --git a/Sources/EFStorageUserDefaults/UserDefaults+RawRepresentable.swift b/Sources/EFStorageUserDefaults/UserDefaults+RawRepresentable.swift
index 866590d..d7998bb 100644
--- a/Sources/EFStorageUserDefaults/UserDefaults+RawRepresentable.swift
+++ b/Sources/EFStorageUserDefaults/UserDefaults+RawRepresentable.swift
@@ -8,7 +8,7 @@
 import Foundation
 
 public extension UserDefaultsStorable where Self: RawRepresentable, Self.RawValue: UserDefaultsStorable {
-    func asUserDefaultsStorable() -> UserDefaultsStorable! {
+    func asUserDefaultsStorable() -> Result<AsIsUserDefaultsStorable, Error> {
         return rawValue.asUserDefaultsStorable()
     }
     static func fromUserDefaults(_ userDefaults: UserDefaults, forKey key: String) -> Self? {