Android : Smart banner container view won't resize

Given the following layout for a content view of a main activity

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:ads="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".CordovaApp"
    tools:ignore="MergeRootFrame" >

    <LinearLayout
        android:id="@+id/layout_main"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical"
        android:layout_above="@+id/layout_ad" >
    </LinearLayout>

    <RelativeLayout
        android:id="@+id/layout_ad"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:orientation="vertical" >

        <com.google.android.gms.ads.AdView
            android:id="@+id/view_ad"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_centerHorizontal="true"
            ads:adSize="SMART_BANNER"
            ads:adUnitId="ca-app-pub-3940256099942544/6300978111" >
        </com.google.android.gms.ads.AdView>
    </RelativeLayout>

</RelativeLayout>

I can't make AdMob's smart banners to work upon orientation change.

If I start in landscape mode, I get a smart banner of height 32. Changing orientation to portrait doesn't change layout_ad height and I get this error

Not enough space to show ad. Needs 480x32 dp, but only has 320x455 dp.