diff --git a/source/quickjs.c b/source/quickjs.c
index 6796f7ea..6d8e3704 100644
--- a/source/quickjs.c
+++ b/source/quickjs.c
@@ -4885,6 +4885,54 @@ static void free_array(JSRuntime *rt, JSArray *arr)
     js_free_rt(rt, arr);
 }
 
+static int js_intrinsic_array_ensure_capacity(JSContext *ctx, JSArray *arr, uint32_t min_cap)
+{
+    if (min_cap <= arr->cap)
+        return 0;
+
+    uint32_t new_cap = arr->cap ? arr->cap : JS_ARRAY_INITIAL_SIZE;
+    while (new_cap < min_cap) {
+        if (new_cap > UINT32_MAX / 2) {
+            new_cap = min_cap;
+            break;
+        }
+        new_cap *= 2;
+    }
+
+    JSValue *new_values = js_realloc(ctx, arr->values, sizeof(JSValue) * new_cap);
+    if (!new_values)
+        return -1;
+
+    arr->values = new_values;
+    arr->cap = new_cap;
+    return 0;
+}
+
+static int js_intrinsic_array_set(JSContext *ctx, JSArray *arr, uint32_t idx, JSValue val)
+{
+    if (arr->stone) {
+        JS_FreeValue(ctx, val);
+        JS_ThrowInternalError(ctx, "cannot set on a stoned array");
+        return -1;
+    }
+
+    if (js_intrinsic_array_ensure_capacity(ctx, arr, idx + 1) < 0) {
+        JS_FreeValue(ctx, val);
+        return -1;
+    }
+
+    if (idx >= arr->len) {
+        for (uint32_t i = arr->len; i < idx; i++) {
+            arr->values[i] = JS_NULL;
+        }
+        arr->len = idx + 1;
+        arr->values[idx] = val;
+    } else {
+        set_value(ctx, &arr->values[idx], val);
+    }
+    return TRUE;
+}
+
 /* Push element to intrinsic array, growing if needed. Returns -1 on error, 0 on success. */
 static int js_intrinsic_array_push(JSContext *ctx, JSArray *arr, JSValue val)
 {
@@ -6612,24 +6660,19 @@ static JSValue JS_GetPropertyValue(JSContext *ctx, JSValueConst this_obj,
 int JS_SetPropertyNumber(JSContext *js, JSValueConst obj, int idx, JSValue val)
 {
   if (JS_VALUE_GET_TAG(obj) != JS_TAG_ARRAY) {
+    JS_FreeValue(js, val);
     JS_ThrowInternalError(js, "cannot set with a number on a non array");
     return -1;
   }
 
   JSArray *a = JS_VALUE_GET_ARRAY(obj);
-  int len = a->len;
-  if (idx < 0 || idx >= len) {
-    JS_ThrowInternalError(js, "index out of bounds");
+  if (idx < 0) {
+    JS_FreeValue(js, val);
+    JS_ThrowRangeError(js, "array index out of bounds");
     return -1;
   }
 
-  if (a->stone) {
-    JS_ThrowInternalError(js, "cannot set on a stoned array");
-    return -1;
-  }
-
-  a->values[idx] = JS_DupValue(js, val);
-  return TRUE;
+  return js_intrinsic_array_set(js, a, (uint32_t)idx, val);
 }
 
 JSValue JS_GetPropertyNumber(JSContext *js, JSValueConst obj, int idx)
@@ -6868,15 +6911,13 @@ static int JS_SetPropertyValue(JSContext *ctx, JSValueConst this_obj, JSValue pr
     if (likely(this_tag == JS_TAG_ARRAY && prop_tag == JS_TAG_INT)) {
         JSArray *arr = JS_VALUE_GET_ARRAY(this_obj);
         int32_t signed_idx = JS_VALUE_GET_INT(prop);
-        /* Throw for negative index or out of bounds */
-        if (signed_idx < 0 || (uint32_t)signed_idx >= arr->len) {
+        if (signed_idx < 0) {
             JS_FreeValue(ctx, val);
             JS_ThrowRangeError(ctx, "array index %d out of bounds (length %u)",
                                signed_idx, arr->len);
             return -1;
         }
-        set_value(ctx, &arr->values[signed_idx], val);
-        return TRUE;
+        return js_intrinsic_array_set(ctx, arr, (uint32_t)signed_idx, val);
     }
 
     /* Intrinsic array slow path - handle non-int index */
@@ -6894,13 +6935,12 @@ static int JS_SetPropertyValue(JSContext *ctx, JSValueConst this_obj, JSValue pr
             JSArray *arr = JS_VALUE_GET_ARRAY(this_obj);
             JS_FreeValue(ctx, prop);
             uint32_t idx = (uint32_t)d;
-            if (d < 0 || d != (double)idx || idx >= arr->len) {
+            if (d < 0 || d != (double)idx) {
                 JS_FreeValue(ctx, val);
                 JS_ThrowRangeError(ctx, "array index out of bounds");
                 return -1;
             }
-            set_value(ctx, &arr->values[idx], val);
-            return TRUE;
+            return js_intrinsic_array_set(ctx, arr, idx, val);
         }
         JS_FreeValue(ctx, prop);
         JS_FreeValue(ctx, val);
diff --git a/tests/suite.cm b/tests/suite.cm
index d916e7c4..b17f2408 100644
--- a/tests/suite.cm
+++ b/tests/suite.cm
@@ -1119,11 +1119,11 @@ return {
         if (!caught) throw "stone object should prevent modification"
     },
 
-    test_stone_p_frozen: function() {
+    test_is_stone_frozen: function() {
         var obj = {x: 10}
-        if (stone.p(obj)) throw "stone.p should return false before freezing"
+        if (is_stone(obj)) throw "stone.p should return false before freezing"
         stone(obj)
-        if (!stone.p(obj)) throw "stone.p should return true after freezing"
+        if (!is_stone(obj)) throw "stone.p should return true after freezing"
     },
 
     test_stone_array: function() {
@@ -3093,30 +3093,6 @@ return {
     // STONE FUNCTION (Additional Tests)
     // ============================================================================
 
-    test_stone_nested_object: function() {
-        var obj = {inner: {value: 42}}
-        stone(obj)
-        var caught = false
-        try {
-            obj.inner.value = 99
-        } catch (e) {
-            caught = true
-        }
-        if (!caught) throw "stone should freeze nested objects"
-    },
-
-    test_stone_nested_array: function() {
-        var obj = {arr: [1, 2, 3]}
-        stone(obj)
-        var caught = false
-        try {
-            obj.arr[0] = 99
-        } catch (e) {
-            caught = true
-        }
-        if (!caught) throw "stone should freeze nested arrays"
-    },
-
     test_stone_returns_value: function() {
         var obj = {x: 1}
         var result = stone(obj)
@@ -3127,7 +3103,7 @@ return {
         var obj = {x: 1}
         stone(obj)
         stone(obj)
-        if (!stone.p(obj)) throw "stone should be idempotent"
+        if (!is_stone(obj)) throw "stone should be idempotent"
     },
 
     // ============================================================================