addColumn problem

I am having a strange problem when trying to add a new column to a database.

If have changeset that has the following property details

1.     <property name="boolean.type" value="boolean" dbms="postgresql, hypersql, hsqldb"/>
       <property name="boolean.type" value="bit" dbms="mysql"/>
       <property name="boolean.type" value="smallint" dbms="derby"/>
       <property name="boolean.type" value="numeric(1)" dbms="oracle"/>

Now if I use the following

1. <changeSet author="UnicentaOpos - John L" id="Create Categories Table">
    <preConditions onFail="MARK_RAN">
       <not>
         <tableExists tableName="CATEGORIES"/>
       </not>
    </preConditions>
2.     <createTable tableName="CATEGORIES">
        <column name="ID" type="varchar(255)">
            <constraints primaryKey="true" nullable="false"/>
           </column>
           <column name="NAME" type="varchar(255)">
            <constraints nullable="false"/>
           </column>
           <column name="PARENTID" type="varchar(255)"/>
           <column name="TEXTTIP" type="varchar(255)" defaultValue="NULL"/>
           <column name="CATSHOWNAME" type="${boolean.type}" defaultValueBoolean="true">
            <constraints nullable="false"/>
           </column>
           <column name="IMAGE" type="${blob.type}"/>
      </createTable>
3. </changeSet>

The table is created ok, but

If a do the following to add the CATSHOWNAME column when it does not exist.

1.  <addColumn tableName="CATEGORIES">
           <column name="CATSHOWNAME" type="${boolean.type}" defaultValueBoolean="true">
            <constraints nullable="false"/>
           </column>
    </addColumn>

I get the error that that smallint can hold the value of type Boolean.

Does any one have any Ideas why this is happening.

Thanks