I am trying to set custom backgrounds for all checkboxes. Here is what I have:

<?xml version="1.0" encoding="UTF-8"?>
<resources>
    <style name="Theme.Foo" parent="@android:style/Theme.Holo.Light.DarkActionBar">
    <item name="android:checkboxStyle">@style/MyCheckbox</item>
    </style>
  <style name="MyCheckbox" parent="@android:style/Widget.CompoundButton.CheckBox">
      <item android:state_checked="true" android:drawable="@drawable/checkboxChecked" /> // unbound prefix error here.
      <item android:state_checked="false" android:drawable="@drawable/checkboxUnchecked" />
  </style>
</resources>

But when I try to build, I get an unbound prefix error on the line for state_checked="true". What am I missing?