expressions conflict with property-placeholder

Is there any work-around for the apparent conflict of expressions with property-placeholders?

e.g. ${header:bar} below causes an error (Could not resolve placeholder 'header:bar'), but if I comment out the <context:property-placeholder> below, and replace ${foo} below with the literal value, then there is not a problem.

        <context:property-placeholder location = "my.properties"/>
...
    <service name = "MyService">    
    <inbound>
                        <vm:inbound-endpoint path = "GetMetadata" />  
    </inbound>    
                        <http:rest-service-component serviceUrl = "${foo}" >
                                <http:requiredParameter key = "name" value = "${header:bar}" />
                        </http:rest-service-component>      
    </service>

Thoughts?

Steve