diff --git a/samples/swift/FirebaseUI-demo-swift/Samples/Auth/FUICustomAuthUIDelegate.swift b/samples/swift/FirebaseUI-demo-swift/Samples/Auth/FUICustomAuthUIDelegate.swift
index 8ad37c3e71..ba83c0118c 100644
--- a/samples/swift/FirebaseUI-demo-swift/Samples/Auth/FUICustomAuthUIDelegate.swift
+++ b/samples/swift/FirebaseUI-demo-swift/Samples/Auth/FUICustomAuthUIDelegate.swift
@@ -20,7 +20,7 @@ import FirebaseEmailAuthUI
 
 class FUICustomAuthDelegate: NSObject, FUIAuthDelegate {
 
-  func authUI(_ authUI: FUIAuth, didSignInWith authDataResult: AuthDataResult?, error: Error?) {
+  @objc func authUI(_ authUI: FUIAuth, didSignInWith authDataResult: AuthDataResult?, error: Error?) {
     switch error {
     case .some(let error as NSError) where UInt(error.code) == FUIAuthErrorCode.userCancelledSignIn.rawValue:
       print("User cancelled sign-in")