Camel Aggregator completionSize does not work with property placeholder

Issue

I have defined a camel route using 'aggregate' tag.

I'd like to make the 'completionSize' dynamic using property placeholder, but It seems it doesn't work.

This is my route:

<route id="my-aggregator">
    <from uri="amq:queue:inputQueue?concurrentConsumers={{concurrent.consumer}}&maxConcurrentConsumers={{concurrent.consumer.max}}" />
    <unmarshal ref="my-json" />
    <process ref="my-processor" />
    <convertBodyTo type="xxx.xxx.xxx.xxx" />
    <aggregate strategyRef="strategy" completionSize="{{completion.size}}" completionTimeout="{{completion.timeout}}">
        <correlationExpression>
            <simple>exit</simple>
        </correlationExpression>
        <to uri="bean:myBean?method=invoke" />
    </aggregate>
    <onException>
    <exception>xxx.xxx.xxx.ValidationException</exception>
    <marshal ref="err-json"/>
    <inOnly uri="amq:queue:deadQueue"/>
    </onException>
</route>

Obviously the property-placeholder element is defined.