How to change PreferenceActivity theme?

I'm trying to change the theme for the PreferenceActivity in my app and I just can't get it to work.

This is the xml:

    <?xml version="1.0" encoding="utf-8"?>
<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android" >

        <SwitchPreference android:title="Auto Clear" android:key="autoclear" android:summary="Clear the command line when the code is being executed." android:defaultValue="false"/>
        <ListPreference android:title="Choose a theme" android:negativeButtonText="" android:dialogTitle="" android:key="theme" android:entries="@array/themesList" android:entryValues="@array/themesList" android:defaultValue="Default" />

</PreferenceScreen>

And this is the PreferenceActivity:

    @Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);

    this.setTheme(R.style.AppTheme);

    addPreferencesFromResource(R.xml.preferences);

}

And the result is: