Id tag with red underline

<LinearLayout xmlns:android="http://ift.tt/nIICcg"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">
    <ListView
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:id="@+id/mylistview"
        android:layout_gravity="center_horizontal"
        />
</LinearLayout>

I've this layout in my project and AndroidStudio underlines in red the part (@+id/mylistview) but everything works fine, I can inflate the XML and also findViewById(R.id.mylistview); Can't figure out the problem, by placing the mouse over I get this message "Top level element is not completed". By changing ListView with ExpandableListView the error disappear.