diff --git a/moli-renderer-v8/src/context_bootstrap/window_accessors.rs b/moli-renderer-v8/src/context_bootstrap/window_accessors.rs
index 6ac98cdedc..5c650b521a 100644
--- a/moli-renderer-v8/src/context_bootstrap/window_accessors.rs
+++ b/moli-renderer-v8/src/context_bootstrap/window_accessors.rs
@@ -24,9 +24,10 @@ pub(super) use helpers::{
     window_child_context_handle, window_has_discarded_child_browsing_context,
 };
 pub(super) use interceptors::{
-    window_indexed_property_deleter, window_indexed_property_descriptor,
-    window_indexed_property_enumerator, window_indexed_property_getter,
-    window_indexed_property_query, window_named_properties_indexed_property_getter,
+    window_indexed_property_definer, window_indexed_property_deleter,
+    window_indexed_property_descriptor, window_indexed_property_enumerator,
+    window_indexed_property_getter, window_indexed_property_query, window_indexed_property_setter,
+    window_named_properties_indexed_property_getter,
     window_named_properties_indexed_property_query, window_named_property_getter,
     window_named_property_query,
 };
diff --git a/moli-renderer-v8/src/context_bootstrap/window_accessors/interceptors.rs b/moli-renderer-v8/src/context_bootstrap/window_accessors/interceptors.rs
index 3173693d96..b91301018b 100644
--- a/moli-renderer-v8/src/context_bootstrap/window_accessors/interceptors.rs
+++ b/moli-renderer-v8/src/context_bootstrap/window_accessors/interceptors.rs
@@ -64,6 +64,17 @@ pub(in crate::context_bootstrap) fn window_indexed_property_getter<'s>(
     v8::Intercepted::kYes
 }
 
+pub(in crate::context_bootstrap) fn window_indexed_property_setter(
+    _scope: &mut v8::PinScope<'_, '_>,
+    _index: u32,
+    _value: v8::Local<'_, v8::Value>,
+    _args: v8::PropertyCallbackArguments<'_>,
+    mut rv: v8::ReturnValue<'_, v8::Boolean>,
+) -> v8::Intercepted {
+    rv.set_bool(false);
+    v8::Intercepted::kYes
+}
+
 pub(in crate::context_bootstrap) fn window_indexed_property_query<'s>(
     scope: &mut v8::PinScope<'s, '_>,
     index: u32,
@@ -77,6 +88,17 @@ pub(in crate::context_bootstrap) fn window_indexed_property_query<'s>(
     v8::Intercepted::kYes
 }
 
+pub(in crate::context_bootstrap) fn window_indexed_property_definer(
+    _scope: &mut v8::PinScope<'_, '_>,
+    _index: u32,
+    _descriptor: &v8::PropertyDescriptor,
+    _args: v8::PropertyCallbackArguments<'_>,
+    mut rv: v8::ReturnValue<'_, v8::Boolean>,
+) -> v8::Intercepted {
+    rv.set_bool(false);
+    v8::Intercepted::kYes
+}
+
 pub(in crate::context_bootstrap) fn window_indexed_property_deleter<'s>(
     scope: &mut v8::PinScope<'s, '_>,
     index: u32,
diff --git a/moli-renderer-v8/src/context_bootstrap/window_template.rs b/moli-renderer-v8/src/context_bootstrap/window_template.rs
index 1d676371ef..66faf5ad3f 100644
--- a/moli-renderer-v8/src/context_bootstrap/window_template.rs
+++ b/moli-renderer-v8/src/context_bootstrap/window_template.rs
@@ -372,9 +372,11 @@ pub(crate) fn install_window_own_template_bindings<'s>(
     window_template.set_indexed_property_handler(
         v8::IndexedPropertyHandlerConfiguration::new()
             .getter(window_indexed_property_getter)
+            .setter(window_indexed_property_setter)
             .query(window_indexed_property_query)
             .deleter(window_indexed_property_deleter)
             .enumerator(window_indexed_property_enumerator)
+            .definer(window_indexed_property_definer)
             .descriptor(window_indexed_property_descriptor),
     );
     // Window is a [Global] WebIDL interface. Blink installs its members on the
diff --git a/moli-renderer-v8/src/script_vm/tests/dom_elements/dom_surface.rs b/moli-renderer-v8/src/script_vm/tests/dom_elements/dom_surface.rs
index a876706fd1..b88abf3575 100644
--- a/moli-renderer-v8/src/script_vm/tests/dom_elements/dom_surface.rs
+++ b/moli-renderer-v8/src/script_vm/tests/dom_elements/dom_surface.rs
@@ -15241,6 +15241,72 @@ fn main_window_indexed_child_deletion_is_live_and_not_cached() {
     );
 }
 
+#[test]
+fn main_window_indexed_set_and_define_reject_every_array_index() {
+    let mut vm = new_storage_test_vm("https://window-indexed-write.test/");
+
+    let result = vm
+        .eval(
+            r#"
+(() => {
+  const frame = document.createElement('iframe');
+  (document.body || document.documentElement || document).appendChild(frame);
+  const child = frame.contentWindow;
+  const strictSetThrows = index => {
+    'use strict';
+    try {
+      window[index] = 'strict';
+      return false;
+    } catch (error) {
+      return error instanceof TypeError;
+    }
+  };
+  const defineThrows = (index, descriptor) => {
+    try {
+      Object.defineProperty(window, index, descriptor);
+      return false;
+    } catch (error) {
+      return error instanceof TypeError;
+    }
+  };
+
+  window[0] = 'sloppy';
+  window[1] = 'sloppy';
+  window[4294967294] = 'sloppy';
+  const result = {
+    existingChildPreserved: window[0] === child,
+    existingStrictSetThrows: strictSetThrows(0),
+    existingReflectSet: Reflect.set(window, 0, 'reflect'),
+    existingReflectDefine: Reflect.defineProperty(window, 0, { value: 'reflect' }),
+    existingDefineThrows: defineThrows(0, { get: () => 'getter' }),
+    missingRemainsAbsent: window[1] === undefined,
+    missingStrictSetThrows: strictSetThrows(1),
+    missingReflectSet: Reflect.set(window, 1, 'reflect'),
+    missingReflectDefine: Reflect.defineProperty(window, 1, { value: 'reflect' }),
+    missingDefineThrows: defineThrows(1, { value: 'defined' }),
+    maxIndexRemainsAbsent: window[4294967294] === undefined,
+    maxIndexStrictSetThrows: strictSetThrows(4294967294),
+    maxIndexReflectSet: Reflect.set(window, 4294967294, 'reflect'),
+    maxIndexReflectDefine: Reflect.defineProperty(window, 4294967294, { value: 'reflect' })
+  };
+  window[4294967295] = 1;
+  result.nonIndexSet = window[4294967295];
+  result.nonIndexReflectSet = Reflect.set(window, 4294967295, 2);
+  result.nonIndexAfterReflectSet = window[4294967295];
+  result.nonIndexReflectDefine = Reflect.defineProperty(window, 4294967295, { value: 3 });
+  result.nonIndexAfterDefine = window[4294967295];
+  return JSON.stringify(result);
+})()
+"#,
+        )
+        .expect("Window indexed write and define probe should evaluate");
+
+    assert_eq!(
+        result,
+        r#"{"existingChildPreserved":true,"existingStrictSetThrows":true,"existingReflectSet":false,"existingReflectDefine":false,"existingDefineThrows":true,"missingRemainsAbsent":true,"missingStrictSetThrows":true,"missingReflectSet":false,"missingReflectDefine":false,"missingDefineThrows":true,"maxIndexRemainsAbsent":true,"maxIndexStrictSetThrows":true,"maxIndexReflectSet":false,"maxIndexReflectDefine":false,"nonIndexSet":1,"nonIndexReflectSet":true,"nonIndexAfterReflectSet":2,"nonIndexReflectDefine":true,"nonIndexAfterDefine":3}"#
+    );
+}
+
 #[tokio::test]
 async fn main_window_indexed_child_descriptor_matches_window_semantics() {
     let mut vm = new_storage_test_vm("https://window-indexed-descriptor.test/");