Why is the exception null when I use onException?

Issue

Why is the exception null when I use onException?

camel route

    <bean class="org.mycompany.MyBean" id="demo"/>
    <camelContext id="cbr-example-context" xmlns="http://camel.apache.org/schema/blueprint">
        <onException>
            <exception>java.lang.IllegalArgumentException</exception>
            <bean method="process" ref="demo"/>
        </onException>
        <route id="cbr-route">
            <from id="route-timer" uri="timer://foo?repeatCount=1"/>
            <setBody id="route-setBody">
                <simple>Hello World from camel-context.xml</simple>
            </setBody>
            <log id="route-log" message=">>> ${body}"/>
            <throwException
                exceptionType="java.lang.IllegalArgumentException"
                id="bugComponent" message="hit the bug"/>
        </route>

Bean

    @Override
    public void process(Exchange exchange) throws Exception {
        Exception exception = exchange.getException();