diff --git a/Source/Turbo/Navigator/Navigator.swift b/Source/Turbo/Navigator/Navigator.swift
index 9c5b0655..05ce60fa 100644
--- a/Source/Turbo/Navigator/Navigator.swift
+++ b/Source/Turbo/Navigator/Navigator.swift
@@ -222,7 +222,11 @@ extension Navigator: SessionDelegate {
     }
 
     public func session(_ session: Session, didReceiveAuthenticationChallenge challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
-        delegate?.didReceiveAuthenticationChallenge(challenge, completionHandler: completionHandler)
+        guard let delegate else {
+            completionHandler(.performDefaultHandling, nil)
+            return
+        }
+        delegate.didReceiveAuthenticationChallenge(challenge, completionHandler: completionHandler)
     }
 
     public func sessionDidFinishRequest(_ session: Session) {
diff --git a/Source/Turbo/Navigator/WKUIController.swift b/Source/Turbo/Navigator/WKUIController.swift
index 0cfb4254..394d4c40 100644
--- a/Source/Turbo/Navigator/WKUIController.swift
+++ b/Source/Turbo/Navigator/WKUIController.swift
@@ -13,14 +13,22 @@ open class WKUIController: NSObject, WKUIDelegate {
     }
 
     open func webView(_ webView: WKWebView, runJavaScriptAlertPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo, completionHandler: @escaping () -> Void) {
+        guard let delegate else {
+            completionHandler()
+            return
+        }
         let alert = UIAlertController(title: message, message: nil, preferredStyle: .alert)
         alert.addAction(UIAlertAction(title: "Close", style: .default) { _ in
             completionHandler()
         })
-        delegate?.present(alert, animated: true)
+        delegate.present(alert, animated: true)
     }
 
     open func webView(_ webView: WKWebView, runJavaScriptConfirmPanelWithMessage message: String, initiatedByFrame frame: WKFrameInfo, completionHandler: @escaping (Bool) -> Void) {
+        guard let delegate else {
+            completionHandler(false)
+            return
+        }
         let alert = UIAlertController(title: message, message: nil, preferredStyle: .alert)
         alert.addAction(UIAlertAction(title: "OK", style: .default) { _ in
             completionHandler(true)
@@ -28,6 +36,6 @@ open class WKUIController: NSObject, WKUIDelegate {
         alert.addAction(UIAlertAction(title: "Cancel", style: .cancel) { _ in
             completionHandler(false)
         })
-        delegate?.present(alert, animated: true)
+        delegate.present(alert, animated: true)
     }
 }
diff --git a/Source/Turbo/Session/Session.swift b/Source/Turbo/Session/Session.swift
index 7aebec5d..483d45b1 100644
--- a/Source/Turbo/Session/Session.swift
+++ b/Source/Turbo/Session/Session.swift
@@ -219,7 +219,11 @@ extension Session: VisitDelegate {
     }
 
     func visit(_ visit: Visit, didReceiveAuthenticationChallenge challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
-        delegate?.session(self, didReceiveAuthenticationChallenge: challenge, completionHandler: completionHandler)
+        guard let delegate else {
+            completionHandler(.performDefaultHandling, nil)
+            return
+        }
+        delegate.session(self, didReceiveAuthenticationChallenge: challenge, completionHandler: completionHandler)
     }
 
     func visitDidProposeVisitToLocation(_ location: URL) {
diff --git a/Source/Turbo/Visit/ColdBootVisit.swift b/Source/Turbo/Visit/ColdBootVisit.swift
index e3e645f2..757eb6c9 100644
--- a/Source/Turbo/Visit/ColdBootVisit.swift
+++ b/Source/Turbo/Visit/ColdBootVisit.swift
@@ -128,7 +128,11 @@ extension ColdBootVisit: WKNavigationDelegate {
     }
 
     func webView(_ webView: WKWebView, didReceive challenge: URLAuthenticationChallenge, completionHandler: @escaping (URLSession.AuthChallengeDisposition, URLCredential?) -> Void) {
-        delegate?.visit(self, didReceiveAuthenticationChallenge: challenge, completionHandler: completionHandler)
+        guard let delegate else {
+            completionHandler(.performDefaultHandling, nil)
+            return
+        }
+        delegate.visit(self, didReceiveAuthenticationChallenge: challenge, completionHandler: completionHandler)
     }
 }