Convert social to military production

I tried to create a durational project that uses the new artifact mechanism that grants production to a shipyard to convert social to military production, but to no avail. That's what I did (values just to test the concept):

  <Improvement>
    <InternalName>AidMilitary</InternalName>
    <DisplayName>Aid Military</DisplayName>
    <ShortDescription>Fuel our shipyard with social production</ShortDescription>
    <Description>Fuel our shipyard with social production</Description>
    <Icon>Aid_Military_Icon.png</Icon>
    <BuildIcon>Aid_Military_Icon.png</BuildIcon>
    <ListIcon>Aid_Military_Icon.png</ListIcon>
    <ImprovementType>DurationalProject</ImprovementType>
    <PlacementType>Special</PlacementType>

    <!-- Stats -->
 
    <Stats>
      <EffectType>ManufacturingCost</EffectType>
      <Scope>Queue</Scope>
      <Target>
        <TargetType>Improvement</TargetType>
      </Target>
      <BonusType>Flat</BonusType>
      <Value>20</Value>
    </Stats>
 
    <!-- Triggers -->
 
    <Triggers>
      <OnEvent>OnConstructImprovment</OnEvent>
      <Scope>Local</Scope>
      <Target>
        <TargetType>Shipyard</TargetType>
      </Target>
      <Lifetime>Instant</Lifetime>
      <Modifier>
        <EffectType>ManufacturingOverflow</EffectType>
        <Target>
          <TargetType>Shipyard</TargetType>
        </Target>
        <BonusType>Flat</BonusType>
        <Value>500</Value>
      </Modifier>
    </Triggers>
 
    <!-- Action Triggers -->
 
    <!-- Level Effect Trigers -->
 
    <!-- Level Effect Stats -->
 
    <!-- Adjacency Bonuses -->
 
    <!-- Prerequisites -->
 
    <Prerequ>
      <Techs>
        <Option>ColonizationTech</Option>
      </Techs>
    </Prerequ>
 
  </Improvement>

Did I miss something? Or is "ManufacturingOverflow" only used in the new artifact code and not in the standard improvement handling code?