Problem changing horse and Polar Bear spawn rates

[Santvarg]

Trying to disable horses and Polarbears with the config entries shown below, yet they still spawn.

  <entry id="horse" mobName="Horse" creatureType="CREATURE" rate="1" remove="true">
    <biomeFilter type="any">
      <biome type="BASE_LAND_TYPES" />
    </biomeFilter>
  </entry>

  <entry id="polarbear" mobName="Polar Bear" creatureType="CREATURE" rate="1" remove="true">
    <biomeFilter type="any">
      <biome type="BASE_LAND_TYPES" />
    </biomeFilter>
  </entry>

I can't find anything wrong with the entries, as the same parameters work for all other Vanilla Monsters and Creatures as far as I can tell. Leads me to believe this is a bug, but if my entries are wrong, do correct me.