diff --git a/auth/cas/auth.php b/auth/cas/auth.php
index eaf3f6c9ffa..22733b2a821 100644
--- a/auth/cas/auth.php
+++ b/auth/cas/auth.php
@@ -187,7 +187,7 @@ class auth_plugin_cas extends auth_plugin_ldap {
         }
 
         // If Moodle is configured to use a proxy, phpCAS needs some curl options set.
-        if (!empty($CFG->proxyhost) && !is_proxybypass($this->config->hostname)) {
+        if (!empty($CFG->proxyhost) && !is_proxybypass(phpCAS::getServerLoginURL())) {
             phpCAS::setExtraCurlOption(CURLOPT_PROXY, $CFG->proxyhost);
             if (!empty($CFG->proxyport)) {
                 phpCAS::setExtraCurlOption(CURLOPT_PROXYPORT, $CFG->proxyport);