diff --git a/src/array.go b/src/array.go
index f949c03..d667bd7 100644
--- a/src/array.go
+++ b/src/array.go
@@ -321,7 +321,7 @@ func ArArray(arr []any) ArObject {
 				}
 			}
 			arr = append(arr, args[0].(ArObject).obj["__value__"].([]any)...)
-			val.obj["length"] = len(arr)
+			val.obj["length"] = newNumber().SetUint64(uint64(len(arr)))
 			val.obj["__value__"] = arr
 			return nil, ArErr{}
 		},
@@ -365,7 +365,7 @@ func ArArray(arr []any) ArObject {
 					return nil, err
 				}
 				arr = output
-				val.obj["length"] = len(arr)
+				val.obj["length"] = newNumber().SetUint64(uint64(len(arr)))
 				val.obj["__value__"] = arr
 				return nil, ArErr{}
 			}
@@ -381,7 +381,7 @@ func ArArray(arr []any) ArObject {
 				}
 			}
 			arr = output
-			val.obj["length"] = len(arr)
+			val.obj["length"] = newNumber().SetUint64(uint64(len(arr)))
 			val.obj["__value__"] = arr
 			return nil, ArErr{}
 		},
diff --git a/src/string.go b/src/string.go
index f056b25..94ec092 100644
--- a/src/string.go
+++ b/src/string.go
@@ -454,7 +454,7 @@ func ArString(str string) ArObject {
 					bytes[i] = b.(byte)
 				}
 				str = string(bytes)
-				obj.obj["length"] = len(str)
+				obj.obj["length"] = newNumber().SetUint64(uint64(len(str)))
 				obj.obj["__value__"] = str
 				return nil, ArErr{}
 			}
@@ -474,7 +474,7 @@ func ArString(str string) ArObject {
 				bytes[i] = b.(byte)
 			}
 			str = string(bytes)
-			obj.obj["length"] = len(str)
+			obj.obj["length"] = newNumber().SetUint64(uint64(len(str)))
 			obj.obj["__value__"] = str
 			return nil, ArErr{}
 		},