Why does hibernate getPropertyNames return an empty list if all attributes are part of the key?

Here's a fun head cleaner to start May in May!

I have a hibernation mapping, for example:

<hibernate-mapping default-lazy="false">
  <class name="my.class.name" table="MY_CLASS_TABLE">
     <composite-id>
       <key-property name="prop1" column="PROP_1" />
       <key-property name="prop2" column="PROP_2" />
       <key-property name="prop3" column="PROP_3" />
     </composite-id>
   </class>
</hibernate-mapping>

And the function that goes through and creates a "dictionary" of class names and properties. I have no problem until I get to this class, and for some reason my call getPropertyNames()returns an empty list. If there is at least one property outside composite-id, I have no problem. I need to add a dummy field outside id (yuck!), And suddenly everything works.

Any idea why this is happening and what I can do to solve it?

Thanks in advance for your help!