diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8ff4704..071a99d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,5 +1,13 @@
 # credential-handler-polyfill ChangeLog
 
+## 4.0.2 - 2026-06-dd
+
+### Fixed
+- Do not throw during `load()` on browsers (e.g., WebKit/iOS) where
+  `navigator.credentials` cannot be redefined via `Object.defineProperty`;
+  fall back to plain assignment or, failing that, skip installing the
+  proxy that protects against subsequent overwrites.
+
 ## 4.0.1 - 2025-12-16
 
 ### Fixed
diff --git a/lib/index.js b/lib/index.js
index 9d15cd0..62be7eb 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -1,5 +1,5 @@
 /*!
- * Copyright (c) 2017-2024 Digital Bazaar, Inc. All rights reserved.
+ * Copyright (c) 2017-2026 Digital Bazaar, Inc.
  */
 /* global navigator, window */
 import {WebAppContext} from 'web-request-rpc';
@@ -104,10 +104,22 @@ export async function load(options = {
     }
   });
 
-  Object.defineProperty(navigator, 'credentials', {
-    value: navCredentialsProxy,
-    writable: true
-  });
+  try {
+    Object.defineProperty(navigator, 'credentials', {
+      value: navCredentialsProxy,
+      writable: true
+    });
+  } catch(e) {
+    // on WebKit, `navigator.credentials` is a non-configurable property
+    // that cannot be redefined as a data property; fall back to plain
+    // assignment and, if that also fails, continue without the proxy --
+    // `get` and `store` have already been replaced on the existing
+    // `navigator.credentials` above, so only the protection against
+    // subsequent overwrites of `navigator.credentials` itself is lost
+    try {
+      navigator.credentials = navCredentialsProxy;
+    } catch(e2) {}
+  }
 
   window.CredentialManager = CredentialManager;
   window.WebCredential = WebCredential;