diff --git a/changelog.d/9579-array-expando-growth.md b/changelog.d/9579-array-expando-growth.md
new file mode 100644
index 0000000000..46178bc8c6
--- /dev/null
+++ b/changelog.d/9579-array-expando-growth.md
@@ -0,0 +1,9 @@
+Named properties attached to arrays remain visible after an indexed write grows
+the array's backing allocation.
+
+The named-property table is keyed by the array header address, while growth
+replaces that header and leaves a forwarding stub behind. Direct runtime
+coverage now pins the required owner transfer to the replacement header and
+asserts that the stale owner is removed. A Node differential also covers typed
+and dynamic arrays through growth, including property enumeration and JSON
+serialization.
diff --git a/crates/perry-runtime/src/array/large_presized_tests.rs b/crates/perry-runtime/src/array/large_presized_tests.rs
index a9ca9b3739..d39d346cbe 100644
--- a/crates/perry-runtime/src/array/large_presized_tests.rs
+++ b/crates/perry-runtime/src/array/large_presized_tests.rs
@@ -4,6 +4,45 @@
 
 use super::*;
 
+// #9201: named properties live in a side table keyed by the array allocation.
+// A grow replaces that allocation, so both the values and the owner key must
+// move before the old header becomes a forwarding stub.
+#[test]
+fn growth_rekeys_named_property_owner() {
+    let _global = crate::gc::global_side_table_test_lock();
+    unsafe {
+        const NAME: &str = "__perry_test_9201_expando__";
+        let key = crate::string::js_string_from_bytes(NAME.as_ptr(), NAME.len() as u32);
+        let mut arr = js_array_alloc(3);
+        arr = js_array_push_f64(arr, 1.0);
+        arr = js_array_push_f64(arr, 2.0);
+        arr = js_array_push_f64(arr, 3.0);
+
+        array_named_property_set(arr, key, 42.0);
+        let old_owner = arr as usize;
+        let old_capacity = (*arr).capacity;
+        assert_eq!(
+            array_named_property_get_by_name(arr, NAME),
+            Some(42.0),
+            "the expando must exist before growth"
+        );
+
+        arr = js_array_set_f64_extend(arr, old_capacity, 99.0);
+
+        assert_ne!(arr as usize, old_owner, "the fixture must grow the array");
+        assert_eq!(
+            array_named_property_get_by_name(arr, NAME),
+            Some(42.0),
+            "#9201: growth must preserve the named property"
+        );
+        assert!(test_array_named_property_owner_exists(arr as usize));
+        assert!(
+            !test_array_named_property_owner_exists(old_owner),
+            "the side table must no longer be keyed by the forwarding stub"
+        );
+    }
+}
+
 #[test]
 fn large_presized_array_grows_its_dense_frontier() {
     unsafe {
diff --git a/crates/perry-runtime/src/array/push_pop.rs b/crates/perry-runtime/src/array/push_pop.rs
index 7beb02cf05..ae5306a8c2 100644
--- a/crates/perry-runtime/src/array/push_pop.rs
+++ b/crates/perry-runtime/src/array/push_pop.rs
@@ -205,7 +205,7 @@ pub extern "C" fn js_array_grow(arr: *mut ArrayHeader, min_capacity: u32) -> *mu
         crate::gc::layout_transfer(arr as *mut u8, new_ptr as *mut u8);
         // Array expandos and sparse numeric indices live in an address-keyed
         // side table. Growth is not a collector move, so rekey it explicitly
-        // before the old address becomes a forwarding stub (#9371).
+        // before the old address becomes a forwarding stub (#9371, #9201).
         transfer_array_named_property_owner(arr as usize, new_ptr as usize);
         // `js_array_grow` is an allocation replacement outside the collector,
         // so GC's normal side-table rekey phase does not run. Preserve every
diff --git a/test-files/test_gap_9201_array_named_properties.ts b/test-files/test_gap_9201_array_named_properties.ts
new file mode 100644
index 0000000000..968c2d3302
--- /dev/null
+++ b/test-files/test_gap_9201_array_named_properties.ts
@@ -0,0 +1,19 @@
+const arr: any[] = [1, 2, 3];
+arr.foo = "bar";
+console.log("before", arr.length, arr.foo, Object.keys(arr).join(","));
+
+arr[10] = "sparse";
+
+console.log("after", arr.length, arr.foo, arr[10]);
+console.log(Object.keys(arr).join(","));
+
+const dynamic: any = [4, 5];
+dynamic.metadata = { total: 2 };
+dynamic["hasMore"] = false;
+console.log("before", dynamic.length, dynamic.metadata.total, dynamic.hasMore);
+
+dynamic[12] = "tail";
+
+console.log("after", dynamic.length, dynamic.metadata.total, dynamic.hasMore, dynamic[12]);
+console.log(Object.keys(dynamic).join(","));
+console.log(JSON.stringify(dynamic));