HAProxy community

How can I verify backend server use root CA file?

	tune.ssl.default-dh-param 2048
	log user
	timeout connect 5000ms
	timeout client 5000ms
	timeout server 5000ms
	mode http
	option httplog
listen reverse-proxy
	acl test_acl hdr_end(host) -i wikipedia.org
	use_backend wikipedia if test_acl
backend wikipedia
	server wikipedia-server ssl verify required ca-file /home/test/haproxy-certificate/GlobalSignRootCA.crt

For example www.wikipedia.org , I try to export the root CA of www.wikipedia.org from Firefox but it doesn’t work and complain with one haproxy 503 page.
If I export the whole certification chain of *.wikipedia.rog it is works, but I just want to verify the root CA because root CA almost never expired.