1 files changed, 14 insertions, 0 deletions
diff --git a/Firebase/Auth/Source/RPCs/FIRAuthBackend.m b/Firebase/Auth/Source/RPCs/FIRAuthBackend.m
index e380e34..ff8f2f0 100644
--- a/Firebase/Auth/Source/RPCs/FIRAuthBackend.m
+++ b/Firebase/Auth/Source/RPCs/FIRAuthBackend.m
@@ -350,6 +350,13 @@ static NSString *const kQuoutaExceededErrorMessage = @"QUOTA_EXCEEDED";
  */
 static NSString *const kAppNotVerifiedErrorMessage = @"APP_NOT_VERIFIED";
 
+/** @var kMissingClientIdentifier
+    @brief This is the error message the server will respond with if Firebase could not verify the
+        app during a phone authentication flow when a real phone number is used and app verification
+        is disabled for testing.
+ */
+static NSString *const kMissingClientIdentifier = @"MISSING_CLIENT_IDENTIFIER";
+
 /** @var kCaptchaCheckFailedErrorMessage
     @brief This is the error message the server will respond with if the reCAPTCHA token provided is
         invalid.
@@ -1073,6 +1080,13 @@ static id<FIRAuthBackendImplementation> gBackendImplementation;
     return [FIRAuthErrorUtils appNotVerifiedErrorWithMessage:serverErrorMessage];
   }
 
+  if ([shortErrorMessage isEqualToString:kMissingClientIdentifier]) {
+    return [FIRAuthErrorUtils appNotVerifiedErrorWithMessage:@"Missing app verification via"
+        " reCAPTCHA or APNS token. Please verify that appVerificationDisabledForTesting is not"
+        " enabled when testing with a phone number that is not marked as a test Phone number in the"
+        " app console."];
+  }
+
   if ([shortErrorMessage isEqualToString:kCaptchaCheckFailedErrorMessage]) {
     return [FIRAuthErrorUtils captchaCheckFailedErrorWithMessage:serverErrorMessage];
   }