Android shadow not work if use alignParentTop

Question

I use this code and shadow work fine:

<carbon.widget.LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentRight="true"
        android:layout_marginLeft="12dp"
        android:layout_marginTop="12dp"
        android:layout_marginRight="12dp"
        android:layout_marginBottom="120dp"
        android:background="@color/colorBgWhite"
        android:clickable="false"
        android:gravity="center|right|center_horizontal"
        app:carbon_cornerRadius="10dp"
        app:carbon_elevation="2.5dp"
        app:carbon_elevationShadowColor="@color/colorShadow">

If I change android:layout_alignParentBottom="true" to android:layout_alignParentTop="true", shadow not work!!

all shadows on top screen not work but in bottom work fine :|

Sample :

screen shot