diff --git a/components/script/window_named_properties.rs b/components/script/window_named_properties.rs
index cccc42750cc..0165e2de625 100644
--- a/components/script/window_named_properties.rs
+++ b/components/script/window_named_properties.rs
@@ -117,14 +117,14 @@ unsafe extern "C" fn get_own_property_descriptor(
         jsstr_to_string(*cx, id.to_string())
     } else if id.is_int() {
         // If the property key is an integer index, convert it to a String too.
-        // TODO(delan) will this interfere with indexed access on the Window object
-        // (window[index]), which should only return document-tree child navigables?
-        // https://html.spec.whatwg.org/multipage/#accessing-other-browsing-contexts
+        // For indexed access on the window object, which may shadow this, see
+        // the getOwnPropertyDescriptor trap in dom/windowproxy.rs.
         id.to_int().to_string()
     } else if id.is_symbol() {
+        // Symbol properties were already handled above.
         unreachable!()
     } else {
-        unreachable!()
+        unimplemented!()
     };
     if s.is_empty() {
         return true;
diff --git a/tests/wpt/web-platform-tests/html/browsers/the-window-object/window-indexed-access-vs-named-access.html b/tests/wpt/web-platform-tests/html/browsers/the-window-object/window-indexed-access-vs-named-access.html
new file mode 100644
index 00000000000..4918d7a5031
--- /dev/null
+++ b/tests/wpt/web-platform-tests/html/browsers/the-window-object/window-indexed-access-vs-named-access.html
@@ -0,0 +1,49 @@
+<!doctype html>
+<meta charset=utf-8>
+<title>Interactions between indexed and named access on the Window object</title>
+<link rel="author" title="Delan Azabani" href="dazabani@igalia.com">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/#accessing-other-browsing-contexts">
+<link rel="help" href="https://html.spec.whatwg.org/multipage/#named-access-on-the-window-object">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<div id=0></div>
+<div id=3></div>
+<iframe name=2></iframe>
+<iframe name=1></iframe>
+<script>
+const divs = document.querySelectorAll("div");
+const iframes = document.querySelectorAll("iframe");
+const wp = Object.getPrototypeOf(window);
+test(function() {
+    assert_equals(window[0], iframes[0].contentWindow);
+    assert_equals(window["0"], iframes[0].contentWindow);
+}, "WindowProxy: document-tree child navigable with index 0 (indexed access)");
+test(function() {
+    assert_equals(window[1], iframes[1].contentWindow);
+    assert_equals(window["1"], iframes[1].contentWindow);
+}, "WindowProxy: document-tree child navigable with index 1 (indexed access)");
+test(function() {
+    assert_equals(window[2], iframes[0].contentWindow);
+    assert_equals(window["2"], iframes[0].contentWindow);
+}, "WindowProxy: document-tree child navigable with target name 2 (named access)");
+test(function() {
+    assert_equals(window[3], divs[1]);
+    assert_equals(window["3"], divs[1]);
+}, "WindowProxy: element with id 3 (named access)");
+test(function() {
+    assert_equals(wp[0], divs[0]);
+    assert_equals(wp["0"], divs[0]);
+}, "Window prototype: element with id 0 (named access)");
+test(function() {
+    assert_equals(wp[1], iframes[1].contentWindow);
+    assert_equals(wp["1"], iframes[1].contentWindow);
+}, "Window prototype: document-tree child navigable with target name 1 (named access)");
+test(function() {
+    assert_equals(wp[2], iframes[0].contentWindow);
+    assert_equals(wp["2"], iframes[0].contentWindow);
+}, "Window prototype: document-tree child navigable with target name 2 (named access)");
+test(function() {
+    assert_equals(wp[3], divs[1]);
+    assert_equals(wp["3"], divs[1]);
+}, "Window prototype: element with id 3 (named access)");
+</script>
