diff --git a/FirebaseMessaging/CHANGELOG.md b/FirebaseMessaging/CHANGELOG.md
index cf83a783db6..795539da1dd 100644
--- a/FirebaseMessaging/CHANGELOG.md
+++ b/FirebaseMessaging/CHANGELOG.md
@@ -1,3 +1,6 @@
+# Unreleased
+- [fixed] Improve token-fetch failure logging with detailed error info. (#13997).
+
 # 11.0.0
 - [fixed] Completed Messaging's transition to NSSecureCoding (#12343).
 
diff --git a/FirebaseMessaging/Sources/Token/FIRMessagingTokenFetchOperation.m b/FirebaseMessaging/Sources/Token/FIRMessagingTokenFetchOperation.m
index ffb3fdb736c..0bc1e79c3b0 100644
--- a/FirebaseMessaging/Sources/Token/FIRMessagingTokenFetchOperation.m
+++ b/FirebaseMessaging/Sources/Token/FIRMessagingTokenFetchOperation.m
@@ -172,6 +172,11 @@ - (void)handleResponseWithData:(NSData *)data
       FIRMessagingLoggerDebug(kFIRMessagingMessageCodeInternal001, @"%@", failureReason);
       responseError = [NSError messagingErrorWithCode:kFIRMessagingErrorCodeInvalidIdentity
                                         failureReason:failureReason];
+    } else {
+      FIRMessagingLoggerDebug(kFIRMessagingMessageCodeTokenFetchOperationRequestError,
+                              @"Token fetch got an error from server: %@", errorValue);
+      responseError = [NSError messagingErrorWithCode:kFIRMessagingErrorCodeUnknown
+                                        failureReason:errorValue];
     }
   }
   if (!responseError) {
diff --git a/FirebaseMessaging/Tests/UnitTests/FIRMessagingTokenOperationsTest.m b/FirebaseMessaging/Tests/UnitTests/FIRMessagingTokenOperationsTest.m
index 0459a8d3e38..a785b7f5b98 100644
--- a/FirebaseMessaging/Tests/UnitTests/FIRMessagingTokenOperationsTest.m
+++ b/FirebaseMessaging/Tests/UnitTests/FIRMessagingTokenOperationsTest.m
@@ -185,7 +185,7 @@ - (void)testThatTokenOperationsAuthHeaderStringMatchesCheckin {
 
   [FIRURLSessionOCMockStub
       stubURLSessionDataTaskWithResponse:expectedResponse
-                                    body:[self dataForResponseWithValidToken:YES]
+                                    body:[self dataForResponseWithValidToken:@""]
                                    error:nil
                           URLSessionMock:self.URLSessionMock
                   requestValidationBlock:^BOOL(NSURLRequest *_Nonnull sentRequest) {
@@ -315,7 +315,7 @@ - (void)testThatOptionsDictionaryIsIncludedWithFetchRequest {
 
   [FIRURLSessionOCMockStub
       stubURLSessionDataTaskWithResponse:expectedResponse
-                                    body:[self dataForResponseWithValidToken:YES]
+                                    body:[self dataForResponseWithValidToken:@""]
                                    error:nil
                           URLSessionMock:self.URLSessionMock
                   requestValidationBlock:^BOOL(NSURLRequest *_Nonnull sentRequest) {
@@ -368,7 +368,7 @@ - (void)testServerResetCommand {
 
   [FIRURLSessionOCMockStub
       stubURLSessionDataTaskWithResponse:expectedResponse
-                                    body:[self dataForResponseWithValidToken:NO]
+                                    body:[self dataForResponseWithValidToken:@"RST"]
                                    error:nil
                           URLSessionMock:self.URLSessionMock
                   requestValidationBlock:^BOOL(NSURLRequest *_Nonnull sentRequest) {
@@ -392,6 +392,55 @@ - (void)testServerResetCommand {
                                }];
 }
 
+- (void)testTooManyRegistrationsError {
+  XCTestExpectation *shouldResetIdentityExpectation =
+      [self expectationWithDescription:@"When server returns TOO_MANY_REGISTRATIONS, the client "
+                                       @"should report the failure reason."];
+  int64_t tenHoursAgo = FIRMessagingCurrentTimestampInMilliseconds() - 10 * 60 * 60 * 1000;
+  FIRMessagingCheckinPreferences *checkinPreferences =
+      [self setCheckinPreferencesWithLastCheckinTime:tenHoursAgo];
+
+  FIRMessagingTokenFetchOperation *operation = [[FIRMessagingTokenFetchOperation alloc]
+      initWithAuthorizedEntity:kAuthorizedEntity
+                         scope:kScope
+                       options:nil
+            checkinPreferences:checkinPreferences
+                    instanceID:self.instanceID
+               heartbeatLogger:[[FIRHeartbeatLoggerFake alloc] init]];
+  NSURL *expectedRequestURL = [NSURL URLWithString:FIRMessagingTokenRegisterServer()];
+  NSHTTPURLResponse *expectedResponse = [[NSHTTPURLResponse alloc] initWithURL:expectedRequestURL
+                                                                    statusCode:200
+                                                                   HTTPVersion:@"HTTP/1.1"
+                                                                  headerFields:nil];
+
+  [FIRURLSessionOCMockStub
+      stubURLSessionDataTaskWithResponse:expectedResponse
+                                    body:[self dataForResponseWithValidToken:
+                                                   @"TOO_MANY_REGISTRATIONS"]
+                                   error:nil
+                          URLSessionMock:self.URLSessionMock
+                  requestValidationBlock:^BOOL(NSURLRequest *_Nonnull sentRequest) {
+                    return YES;
+                  }];
+
+  [operation addCompletionHandler:^(FIRMessagingTokenOperationResult result,
+                                    NSString *_Nullable token, NSError *_Nullable error) {
+    XCTAssertEqual(result, FIRMessagingTokenOperationError);
+    XCTAssertNotNil(error);
+    XCTAssertEqual(error.code, kFIRMessagingErrorCodeUnknown);
+    XCTAssertEqualObjects(error.localizedFailureReason, @"TOO_MANY_REGISTRATIONS");
+
+    [shouldResetIdentityExpectation fulfill];
+  }];
+
+  [operation start];
+
+  [self waitForExpectationsWithTimeout:0.25
+                               handler:^(NSError *_Nullable error) {
+                                 XCTAssertNil(error.localizedDescription);
+                               }];
+}
+
 - (void)testHTTPAuthHeaderGenerationFromCheckin {
   FIRMessagingCheckinPreferences *checkinPreferences =
       [[FIRMessagingCheckinPreferences alloc] initWithDeviceID:kDeviceID secretToken:kSecretToken];
@@ -447,7 +496,7 @@ - (void)assertTokenFetchOperationRequestContainsFirebaseUserAgentAndHeartbeatInf
 
   [FIRURLSessionOCMockStub
       stubURLSessionDataTaskWithResponse:expectedResponse
-                                    body:[self dataForResponseWithValidToken:NO]
+                                    body:[self dataForResponseWithValidToken:@"RST"]
                                    error:nil
                           URLSessionMock:self.URLSessionMock
                   requestValidationBlock:^BOOL(NSURLRequest *_Nonnull sentRequest) {
@@ -471,12 +520,12 @@ - (void)assertTokenFetchOperationRequestContainsFirebaseUserAgentAndHeartbeatInf
                                }];
 }
 
-- (NSData *)dataForResponseWithValidToken:(BOOL)validToken {
+- (NSData *)dataForResponseWithValidToken:(NSString *)errorCode {
   NSString *response;
-  if (validToken) {
+  if (errorCode.length == 0) {
     response = [NSString stringWithFormat:@"token=%@", kRegistrationToken];
   } else {
-    response = @"Error=RST";
+    response = [NSString stringWithFormat:@"Error=%@", errorCode];
   }
   return [response dataUsingEncoding:NSUTF8StringEncoding];
 }