Enabling JSF 2.3 in IntelliJ

Hi,

As Primefaces are deprecating their Push api I'm looking at using native JSF 2.3 websockets. However, in IntelliJ on my JSF pages f:websocket gives "Cannot resolve symbol". I am using Glassfish 5, and have java EE 8 in my pom along with javaxfaces version 2.4.0. I have changed my faces config to:

<?xml version='1.0' encoding='UTF-8'?>
<faces-config version="2.3" xmlns="http://xmlns.jcp.org/xml/ns/javaee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee 
    http://xmlns.jcp.org/xml/ns/javaee/web-facesconfig_2_3.xsd">
    <lifecycle>
        <phase-listener>myprogram.util.PhaseTracker</phase-listener>
    </lifecycle>
</faces-config>


I also have this in my web.xml

<context-param>
    <param-name>javax.faces.ENABLE_WEBSOCKET_ENDPOINT</param-name>
    <param-value>true</param-value>
</context-param>

I'm not sure what else I need to set up so websocket is resolved. Does anybody have any ideas?

Thanks,
Ian