activemq queue maxConcurrentConsumers does not scale down.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xmlns:camel="http://camel.apache.org/schema/spring"
       xsi:schemaLocation="
       http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
       http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">

     <!-- lets configure the Camel ActiveMQ to use the embedded ActiveMQ broker declared above -->
     <bean id="amq" class="org.apache.activemq.camel.component.ActiveMQComponent">
        <property name="brokerURL" value="tcp://localhost:61616?jms.prefetchPolicy.all=1"/>
        <property name="userName" value="admin"/>
        <property name="password" value="admin"/>
        <property name="concurrentConsumers" value="4"/>
        <property name="maxConcurrentConsumers" value="12" />
        <property name="requestTimeoutCheckerInterval" value="1000" />
        <property name="requestTimeout" value="10000" />
    </bean>

    <camel:camelContext xmlns="http://camel.apache.org/schema/spring">
      <camel:route>
        <camel:from uri="amq:queue:FOO.BAR" />
        <camel:setBody>
            <camel:simple>Hello from Camel route</camel:simple>
        </camel:setBody>
        <camel:log message="Received payload2: ${body}"/>
      </camel:route>
    </camel:camelContext>

</beans>