Expandablelistview background gets whiter when i expand child row

Expandablelistview's background gets whiter as I expand the child rows. How can I fix this?

I have installed:

android:cacheColorHint="@null"
android:scrollingCache="false"

      

        
        
        
      

    

I've also tried:

android:cacheColorHint="@android:color/transparent"
android:scrollingCache="false"

      

        
        
        
      

    

But the problem persists.

Screenshot before expanding the child:

http://i.imgur.com/fbaKPus.png http://i.imgur.com/pHejwDn.png

after

http://i.imgur.com/hftsxhA.png

EDIT:

The app uses the Sherlock theme: ...   

Expandablelistview extension file:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <ExpandableListView
        android:id="@+id/expandableListView"
        android:layout_width="match_parent"
        android:layout_height="fill_parent"
        android:background="@drawable/background"
        android:cacheColorHint="@android:color/transparent"
        android:childDivider="@color/expandablelist_divider"
        android:divider="@color/expandablelist_divider"
        android:dividerHeight="1dp"
        android:groupIndicator="@drawable/expandablelistindicator" >
    </ExpandableListView>

</LinearLayout>