Make backup agent run in the system process as well.

    <application android:allowClearUserData="false"

                 android:label="@string/app_label"

                 android:process="system"

                 android:backupAgent="SettingsBackupAgent"

                 android:icon="@drawable/ic_launcher_settings">

        <provider android:name="SettingsProvider" android:authorities="settings"

                  android:process="system" android:multiprocess="false"

                  android:multiprocess="false"

                  android:writePermission="android.permission.WRITE_SETTINGS"

                  android:initOrder="100" />

    </application>