Changing background of drawable instance in ListView

I have a drawable resource drawable/badge.xml which looks like this:

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://ift.tt/nIICcg" android:shape="oval" >
    <solid android:color="#000" />
</shape>

...and is used inside a layout file layout/badge.xml which looks like this:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://ift.tt/nIICcg"
    android:layout_width="18dp"
    android:layout_height="18dp" >

    <View
        android:id="@+id/badge"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:background="@drawable/badge" />

    <TextView
        android:id="@+id/badge_text"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center_vertical|center_horizontal"
        android:textColor="#fff"
        android:textSize="12sp"
        android:textStyle="bold" />

</RelativeLayout>

Inside a BaseExpandableListAdapters getChildView method there is this code:

...
LinearLayout badgeContainer = (LinearLayout) convertView.findViewById(R.id.badge_container);
for (String property : properties) {

    RelativeLayout badge = (RelativeLayout) inflater.inflate(R.layout.badge, badgeContainer, false);

    badge.setLayoutParams(new LinearLayout.LayoutParams(50, 50));

    ((TextView) badge.findViewById(R.id.badge_text)).setText(course.property);
    badge.findViewById(R.id.badge).getBackground().setColorFilter(getColorResourceByProperty(property), PorterDuff.Mode.DST);

    badgeContainer.addView(badge);
}
...

So what I'm trying to do is change the background color of the drawable badge for each property, but this code still yields in all badges to have a black background. What am I doing wrong? I've also tried many other PorterDuff modes without results.