diff --git a/CHANGELOG.md b/CHANGELOG.md
index 3a111c4..11eb79f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,14 @@
 # Changelog
 
+## Version 4.0.0
+- Support Retention Messaging API [https://github.com/apple/app-store-server-library-swift/pull/101]
+  - This changes internal details of AppStoreServerAPIClient, which is a breaking change for subclassing clients
+- Incorporate changes for App Store Server API v1.17 [https://github.com/apple/app-store-server-library-swift/pull/102] from @riyazpanjwani
+- Add a new VerificationError case for retryable OCSP network failures [https://github.com/apple/app-store-server-library-swift/pull/104]
+- Incorporate changes for App Store Server API v1.18 [https://github.com/apple/app-store-server-library-swift/pull/106] from @izanger
+  - This changes OfferType's case subscriptionOfferCode to offerCode, which is a breaking change
+- Fix Base64URL decoding [https://github.com/apple/app-store-server-library-swift/pull/107] from @shimastripe
+
 ## Version 3.1.0
 - Incorporate changes for App Store Server API v1.16 [https://github.com/apple/app-store-server-library-swift/pull/89]
 - Update Swift docs to v6 [https://github.com/apple/app-store-server-library-swift/pull/85]
diff --git a/README.md b/README.md
index 9303cfa..576024b 100644
--- a/README.md
+++ b/README.md
@@ -16,7 +16,7 @@ The Swift server library for the [App Store Server API](https://developer.apple.
 ### Swift Package Manager
 Add the following dependency
 ```swift
-.package(url: "https://github.com/apple/app-store-server-library-swift.git", .upToNextMinor(from: "3.1.0")),
+.package(url: "https://github.com/apple/app-store-server-library-swift.git", .upToNextMinor(from: "4.0.0")),
 ```
 
 ## Documentation
diff --git a/Sources/AppStoreServerLibrary/AppStoreServerAPIClient.swift b/Sources/AppStoreServerLibrary/AppStoreServerAPIClient.swift
index ccea0fa..7d8c125 100644
--- a/Sources/AppStoreServerLibrary/AppStoreServerAPIClient.swift
+++ b/Sources/AppStoreServerLibrary/AppStoreServerAPIClient.swift
@@ -14,7 +14,7 @@ public actor AppStoreServerAPIClient: Sendable {
         case invalidEnvironment
     }
     
-    private static let userAgent = "app-store-server-library/swift/3.1.0"
+    private static let userAgent = "app-store-server-library/swift/4.0.0"
     private static let productionUrl = "https://api.storekit.itunes.apple.com"
     private static let sandboxUrl = "https://api.storekit-sandbox.itunes.apple.com"
     private static let localTestingUrl = "https://local-testing-base-url"