diff --git a/FirebaseMessaging/Apps/Sample/Sample/SceneDelegate.swift b/FirebaseMessaging/Apps/Sample/Sample/SceneDelegate.swift
index 9da2899bb3b..bf65d4ac848 100644
--- a/FirebaseMessaging/Apps/Sample/Sample/SceneDelegate.swift
+++ b/FirebaseMessaging/Apps/Sample/Sample/SceneDelegate.swift
@@ -72,7 +72,7 @@ class SceneDelegate: UIResponder, UIWindowSceneDelegate, MessagingDelegate {
       .store(in: &cancellables)
   }
 
-  func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String) {
+  func messaging(_ messaging: Messaging, didReceiveRegistrationToken fcmToken: String?) {
     identity.token = fcmToken
   }
 }
diff --git a/FirebaseMessaging/CHANGELOG.md b/FirebaseMessaging/CHANGELOG.md
index 7ae7dbd7096..42198a39238 100644
--- a/FirebaseMessaging/CHANGELOG.md
+++ b/FirebaseMessaging/CHANGELOG.md
@@ -1,5 +1,6 @@
 # unreleased -- v.7.0.0
 - [changed] Remove the deprecated FCM direct channel API and Upstream send API. (#6430)
+- [changed] The `messaging:didReceiveRegistrationToken:` should be able to return a null token. Update the API parameter fcmToken to be nullable. (#5339)
 - [fixed] Fixed an issue that downloading an image failed when there's no extension in the file name but MIME type is set. (#6590)
 
 # 2020-09 -- v.4.7.1
diff --git a/FirebaseMessaging/Sources/Public/FirebaseMessaging/FIRMessaging.h b/FirebaseMessaging/Sources/Public/FirebaseMessaging/FIRMessaging.h
index 8edcea4aaa5..0a22dae6169 100644
--- a/FirebaseMessaging/Sources/Public/FirebaseMessaging/FIRMessaging.h
+++ b/FirebaseMessaging/Sources/Public/FirebaseMessaging/FIRMessaging.h
@@ -146,7 +146,7 @@ NS_SWIFT_NAME(MessagingDelegate)
 ///
 /// * Subscribing to any topics.
 - (void)messaging:(FIRMessaging *)messaging
-    didReceiveRegistrationToken:(NSString *)fcmToken
+    didReceiveRegistrationToken:(nullable NSString *)fcmToken
     NS_SWIFT_NAME(messaging(_:didReceiveRegistrationToken:));
 @end
 
diff --git a/FirebaseMessaging/Tests/IntegrationTests/FIRMessagingTokenRefreshTests.swift b/FirebaseMessaging/Tests/IntegrationTests/FIRMessagingTokenRefreshTests.swift
index ed8cf1dfc16..6506911b174 100644
--- a/FirebaseMessaging/Tests/IntegrationTests/FIRMessagingTokenRefreshTests.swift
+++ b/FirebaseMessaging/Tests/IntegrationTests/FIRMessagingTokenRefreshTests.swift
@@ -28,7 +28,7 @@
     var messaging = Messaging.messaging()
     var delegateIsCalled = false
 
-    func messaging(_: Messaging, didReceiveRegistrationToken _: String) {
+    func messaging(_: Messaging, didReceiveRegistrationToken _: String?) {
       delegateIsCalled = true
     }
   }