I have a many to many mapping based on the documentation. I cannot get it to work at all. I am getting the error message:

Foreign key in table LicensedFeatures must have same number of columns as referenced primary key in table Configurations

Configurations has a primary key called Id
Features has a primary key called Id
The mapping table LicensedFeatures has two columns: ConfigurationId and FeatureId. These have foreign key constraints to the Id columns in the other tables.

My mapping files look like this:

Configuration.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
namespace="ActivationAdmin" assembly="ActivationAdmin">
<class name="Configuration" table="Configurations">
<id name="Id" type="Int64" column="Id" unsaved-value="0">
<generator class="identity"/>
</id>
<set name="LicensedFeatures" lazy="true" table="LicensedFeatures">
<key column="ConfigurationId"/>
<many-to-many class="Feature" column="FeatureId"/>
</set>
</class>
</hibernate-mapping>

Feature.hbm.xml

<?xml version="1.0" encoding="utf-8" ?>
<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2"
namespace="ActivationAdmin" assembly="ActivationAdmin">
<class name="Feature" table="Features">
<id name="Id" type="Int64" column="Id" unsaved-value="0">
<generator class="identity"/>
</id>
<property name="FeatureName" column="FeatureName" length="50" not-null="true" />
</class>
</hibernate-mapping>


When I try and use this I get an exception saying:

Foreign key in table LicensedFeatures must have same number of columns as referenced primary key in table Configurations

I am tearing my hair out.