diff --git a/authentication/LegacyAuthQuickstart/AuthenticationExample/PasswordlessViewController.m b/authentication/LegacyAuthQuickstart/AuthenticationExample/PasswordlessViewController.m
index dbe167c69..a5a12e2d0 100644
--- a/authentication/LegacyAuthQuickstart/AuthenticationExample/PasswordlessViewController.m
+++ b/authentication/LegacyAuthQuickstart/AuthenticationExample/PasswordlessViewController.m
@@ -70,6 +70,7 @@ - (IBAction)didTapSendSignInLink:(id)sender {
     [actionCodeSettings setURL:[NSURL URLWithString:@"https://www.example.com"]];
     // The sign-in operation has to always be completed in the app.
     actionCodeSettings.handleCodeInApp = YES;
+    actionCodeSettings.linkDomain = @"your.custom.domain.com";
     [actionCodeSettings setIOSBundleID:[[NSBundle mainBundle] bundleIdentifier]];
     [actionCodeSettings setAndroidPackageName:@"com.example.android"
                         installIfNotAvailable:NO
diff --git a/authentication/LegacyAuthQuickstart/AuthenticationExampleSwift/PasswordlessViewController.swift b/authentication/LegacyAuthQuickstart/AuthenticationExampleSwift/PasswordlessViewController.swift
index b20fa588e..d91c15eea 100644
--- a/authentication/LegacyAuthQuickstart/AuthenticationExampleSwift/PasswordlessViewController.swift
+++ b/authentication/LegacyAuthQuickstart/AuthenticationExampleSwift/PasswordlessViewController.swift
@@ -66,6 +66,7 @@ class PasswordlessViewController: UIViewController {
         actionCodeSettings.url = URL(string: "https://www.example.com")
         // The sign-in operation has to always be completed in the app.
         actionCodeSettings.handleCodeInApp = true
+        actionCodeSettings.linkDomain = "your.custom.domain.com"
         actionCodeSettings.setIOSBundleID(Bundle.main.bundleIdentifier!)
         actionCodeSettings.setAndroidPackageName("com.example.android",
                                                  installIfNotAvailable: false, minimumVersion: "12")