Unrecognized element <vpc-access-connector> when deploying AppEngine Java8

Question

Having the following error when trying to deploy AppEngine with Java8:

Execution failed for task ':endpoints:endpointsDiscoveryDocs'.
> Unrecognized element <vpc-access-connector>

This element is available since 2019 and I'm using a recent version of appengine.

here is part of the appengine-web.xml

<?xml version="1.0" encoding="utf-8"?>
<appengine-web-app xmlns="http://appengine.google.com/ns/1.0">
    <threadsafe>true</threadsafe>
    <instance-class>F4</instance-class>
    <runtime>java8</runtime>
    <vpc-access-connector>
        <name>name</name>
        <egress-setting>private-ranges-only</egress-setting>
    </vpc-access-connector>

any ideas what might be wrong?