is_old_value_copyable&lt;T&gt;::value</code> is <code class="computeroutput">true</code>. A copyable old value type <code class="computeroutput">V</code> is always copied using <code class="computeroutput">boost::contract::old_value_copy&lt;V&gt;</code>. A non-copyable old value type <code class="computeroutput">W</code> generates a compile-time error when <code class="computeroutput">boost::contract::old_ptr&lt;W&gt;</code> is dereferenced, but instead leaves <code class="computeroutput">boost::contract::o