diff --git a/test/staging/built-ins/Array/prototype/flatMap/callback-with-side-effects.js b/test/staging/built-ins/Array/prototype/flatMap/callback-with-side-effects.js
new file mode 100644
index 0000000000..ac98b5d215
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+++ b/test/staging/built-ins/Array/prototype/flatMap/callback-with-side-effects.js
@@ -0,0 +1,28 @@
+// Copyright (C) 2024 the V8 project authors. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+
+/*---
+esid: sec-array.prototype.flatMap
+description: >
+  Array.prototype.flatMap is given a callback that modifies the array being
+  iterated.
+includes: [compareArray.js]
+---*/
+
+(function TestGrow() {
+  let array = [0,1,2,3];
+  function f(e) {
+    array[4] = 42;
+    return e;
+  }
+  assert.compareArray(array.flatMap(f), [0,1,2,3]);
+})();
+
+(function TestShrink() {
+  let array = [0,1,2,3];
+  function f(e) {
+    array.length = 3;
+    return e;
+  }
+  assert.compareArray(array.flatMap(f), [0,1,2]);
+})();