diff --git a/cas.admin.inc b/cas.admin.inc
index ebbb396..0fa049a 100644
--- a/cas.admin.inc
+++ b/cas.admin.inc
@@ -63,7 +63,7 @@ function cas_admin_settings() {
     '#size' => 30,
     // Hostnames can be 255 characters long.
     '#maxlength' => 255,
-    '#description' => t('Hostname or IP Address of the CAS server.'),
+    '#description' => t('Hostname or IP Address of the CAS server. CAS logins will not work until this hostname is entered.'),
   );
 
   $form['server']['cas_port'] = array(
diff --git a/cas.install b/cas.install
index eb08961..3273e6b 100644
--- a/cas.install
+++ b/cas.install
@@ -149,6 +149,13 @@ function cas_requirements($phase) {
 }
 
 /**
+ * Implements hook_enable().
+ */
+function cas_enable() {
+  drupal_set_message(t('CAS has been enabled. Please <a href="@url">configure</a> it.', array('@url' => url('admin/config/people/cas'))), 'warning');
+}
+
+/**
  * Creates CAS login data table for Single-Sign-Out.
  */
 function cas_update_1() {
diff --git a/cas.module b/cas.module
index a4119bb..b9720f9 100644
--- a/cas.module
+++ b/cas.module
@@ -79,8 +79,10 @@ function cas_login_check($force_authentication = TRUE) {
   drupal_session_start();
   _cas_single_sign_out_save_ticket();  // We use this later for CAS 3 logoutRequests
 
-  // Initialize phpCAS.
-  cas_phpcas_init();
+  // Initialize phpCAS if possible, otherwise just back out.
+  if (cas_phpcas_init() === FALSE) {
+    return;
+  }
 
   // We're going to try phpCAS auth test
   if ($force_authentication) {
@@ -252,11 +254,19 @@ function cas_phpcas_init() {
 
   // Variable set
   $server_version    = (string)variable_get('cas_version', '3.0');
-  $server_cas_server = (string)variable_get('cas_server', 'sso-cas.univ-rennes1.fr');
+  $server_cas_server = (string)variable_get('cas_server', '');
   $server_port       = (int)variable_get('cas_port', '443');
   $server_uri        = (string)variable_get('cas_uri', '');
   $cas_cert          = (string)variable_get('cas_cert', '');
   $debug_file        = (string)variable_get('cas_debugfile', '');
+
+  // Back out if there's no configured CAS server hostname. This is the
+  // minimum required configuration to initialize phpCAS.
+  if (empty($server_cas_server)) {
+    watchdog('cas', 'Unable to initialize phpCAS because no CAS server hostname has been configured.', array(), WATCHDOG_ERROR);
+    return FALSE;
+  }
+
   if ($debug_file != '') {
     phpCAS::setDebug($debug_file);
   }
diff --git a/cas.test b/cas.test
index dde3213..351d756 100644
--- a/cas.test
+++ b/cas.test
@@ -31,6 +31,9 @@ class CasTestHelper extends DrupalWebTestCase {
     // in phpCAS.
     variable_set('clean_url', TRUE);
 
+    // Set CAS server url (will be altered).
+    variable_set('cas_server', 'example.com');
+
     // Create admin user.
     $this->admin_user = $this->drupalCreateUser(array('administer users', 'administer cas'));