diff --git a/content/browser/service_worker/service_worker_main_resource_handle.cc b/content/browser/service_worker/service_worker_main_resource_handle.cc
index 4cd3f0044247e..5942495d9aafc 100644
--- a/content/browser/service_worker/service_worker_main_resource_handle.cc
+++ b/content/browser/service_worker/service_worker_main_resource_handle.cc
@@ -109,6 +109,15 @@ bool ServiceWorkerMainResourceHandle::InitializeForRequest(
         client_for_prefetch->key() != key) {
       return false;
     }
+    // The prefetch's ServiceWorkerClient must belong to the same
+    // ServiceWorkerContext (and hence the same StoragePartition) as this
+    // navigation handle. The prefetch client is always created from the
+    // default StoragePartition (PrefetchStreamingURLLoader), while
+    // `context_wrapper_` reflects the navigation's actual partition (e.g. a
+    // <webview>/Controlled Frame guest partition).
+    if (client_for_prefetch->context().get() != context_wrapper_->context()) {
+      return false;
+    }
   }
 
   isolation_info_ = std::move(new_isolation_info);