diff --git a/Libraries/LibWeb/HTML/Navigable.cpp b/Libraries/LibWeb/HTML/Navigable.cpp
index faa3d04842..7efafd7491 100644
--- a/Libraries/LibWeb/HTML/Navigable.cpp
+++ b/Libraries/LibWeb/HTML/Navigable.cpp
@@ -2014,12 +2014,12 @@ void Navigable::begin_navigation(NavigateParams params)
     if (!active_window())
         return;
 
-    auto const& url = params.url;
+    auto url = params.url;
     auto source_document = params.source_document;
-    auto const& document_resource = params.document_resource;
+    auto document_resource = params.document_resource;
     auto response = params.response;
     auto history_handling = params.history_handling;
-    auto const& navigation_api_state = params.navigation_api_state;
+    auto navigation_api_state = params.navigation_api_state;
     auto referrer_policy = params.referrer_policy;
     auto user_involvement = params.user_involvement;
     auto source_element = params.source_element;
@@ -2133,6 +2133,7 @@ void Navigable::begin_navigation(NavigateParams params)
         // AD-HOC: The HTML Standard cancels a navigation that starts while a traversal is ongoing. We defer it
         //         instead so UI-initiated navigations that race the tail end of a previous load are not dropped.
         //         Match Chromium, WebKit, and Gecko's observable behavior by letting the newest navigation win.
+        //         See https://github.com/whatwg/html/issues/12581.
         queue_pending_navigation(move(params), PendingNavigationBehavior::Replace);
 
         // 2. Return.
@@ -2201,7 +2202,7 @@ void Navigable::begin_navigation(NavigateParams params)
     // FIXME: 22. If sourceDocument is navigable's container document, then reserve deferred fetch quota for navigable's container given url's origin.
 
     // 23. In parallel, run these steps:
-    Platform::EventLoopPlugin::the().deferred_invoke(GC::create_function(heap(), [this, source_snapshot_params, target_snapshot_params, csp_navigation_type, document_resource, url, navigation_id, referrer_policy, initiator_origin_snapshot, response, history_handling, initiator_base_url_snapshot, user_involvement] {
+    Platform::EventLoopPlugin::the().deferred_invoke(GC::create_function(heap(), [this, source_snapshot_params, target_snapshot_params, csp_navigation_type, document_resource, url, navigation_id, referrer_policy, initiator_origin_snapshot, response, history_handling, initiator_base_url_snapshot, user_involvement, params = move(params)] mutable {
         // AD-HOC: Not in the spec but subsequent steps will fail if the navigable doesn't have an active window.
         if (!active_window()) {
             set_delaying_load_events(false);
@@ -2210,7 +2211,7 @@ void Navigable::begin_navigation(NavigateParams params)
 
         // 1. Let unloadPromptCanceled be the result of checking if unloading is user-canceled for navigable's active document's inclusive descendant navigables.
         traversable_navigable()->check_if_unloading_is_canceled(this->active_document()->inclusive_descendant_navigables(),
-            GC::create_function(heap(), [this, source_snapshot_params, target_snapshot_params, csp_navigation_type, document_resource, url, navigation_id, referrer_policy, initiator_origin_snapshot, response, history_handling, initiator_base_url_snapshot, user_involvement](TraversableNavigable::CheckIfUnloadingIsCanceledResult unload_prompt_canceled) {
+            GC::create_function(heap(), [this, source_snapshot_params, target_snapshot_params, csp_navigation_type, document_resource, url, navigation_id, referrer_policy, initiator_origin_snapshot, response, history_handling, initiator_base_url_snapshot, user_involvement, params = move(params)](TraversableNavigable::CheckIfUnloadingIsCanceledResult unload_prompt_canceled) mutable {
                 // 2. If unloadPromptCanceled is not "continue", or navigable's ongoing navigation is no longer navigationId:
                 if (unload_prompt_canceled != TraversableNavigable::CheckIfUnloadingIsCanceledResult::Continue) {
                     // FIXME: 1. Invoke WebDriver BiDi navigation failed with navigable and a new WebDriver BiDi navigation status whose id is navigationId, status is "canceled", and url is url.
@@ -2234,6 +2235,13 @@ void Navigable::begin_navigation(NavigateParams params)
                 }
 
                 if (ongoing_navigation() != navigation_id) {
+                    // AD-HOC: If an ongoing traversal re-stamped our navigation ID while we were checking whether
+                    //         unloading was canceled, this navigation wasn't actually superseded by a newer navigation.
+                    //         Re-defer it (mirroring 66c54b129514), so it runs once the traversal completes — rather
+                    //         than silently dropping it and leaving the navigable stuck with no load event ever firing.
+                    //         See https://github.com/whatwg/html/issues/12581.
+                    if (ongoing_navigation().has<Traversal>())
+                        queue_pending_navigation(move(params), PendingNavigationBehavior::Append);
                     set_delaying_load_events(false);
                     return;
                 }
diff --git a/Tests/LibWeb/Text/expected/navigation/navigation-not-dropped-by-concurrent-traversal.txt b/Tests/LibWeb/Text/expected/navigation/navigation-not-dropped-by-concurrent-traversal.txt
new file mode 100644
index 0000000000..e33bed7c2f
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/navigation/navigation-not-dropped-by-concurrent-traversal.txt
@@ -0,0 +1 @@
+victim-loaded
diff --git a/Tests/LibWeb/Text/input/navigation/navigation-not-dropped-by-concurrent-traversal.html b/Tests/LibWeb/Text/input/navigation/navigation-not-dropped-by-concurrent-traversal.html
new file mode 100644
index 0000000000..e63af28b3e
--- /dev/null
+++ b/Tests/LibWeb/Text/input/navigation/navigation-not-dropped-by-concurrent-traversal.html
@@ -0,0 +1,47 @@
+<!DOCTYPE html>
+<script src="../include.js"></script>
+<script>
+    // A cross-document navigation must not be silently dropped when a concurrent session-history traversal re-stamps
+    // the navigable's ongoing navigation while the cross-document load is still in its unload check.
+    // clobberNextNavigationWithATraversal() arms a one-shot that deterministically interrupts the next navigation's
+    // unload check with a synthetic traversal; the navigation must still run to completion instead of being dropped.
+    asyncTest(async (done) => {
+        const server = httpTestServer();
+
+        const victim = await server.createEcho("GET", "/navigation-not-dropped-by-concurrent-traversal-victim", {
+            status: 200,
+            headers: { "Content-Type": "text/html" },
+            body: `<!doctype html><script>top.postMessage("victim-loaded", "*")<\/script>`,
+        });
+
+        const trigger = await server.createEcho("GET", "/navigation-not-dropped-by-concurrent-traversal-trigger", {
+            status: 200,
+            headers: { "Content-Type": "text/html" },
+            body: `<!doctype html><script>
+                addEventListener("message", (e) => { if (e.data === "go") location.href = "${victim}"; });
+                top.postMessage("trigger-ready", "*");
+            <\/script>`,
+        });
+
+        let iframe;
+        let stallTimer;
+        window.addEventListener("message", (e) => {
+            if (e.data === "trigger-ready") {
+                internals.clobberNextNavigationWithATraversal();
+                iframe.contentWindow.postMessage("go", "*");
+                stallTimer = setTimeout(() => {
+                    println("FAIL: cross-document navigation was dropped");
+                    done();
+                }, 10000);
+            } else if (e.data === "victim-loaded") {
+                clearTimeout(stallTimer);
+                println("victim-loaded");
+                done();
+            }
+        });
+
+        iframe = document.createElement("iframe");
+        iframe.src = trigger;
+        document.body.appendChild(iframe);
+    });
+</script>