diff --git a/session_limit.install b/session_limit.install
index a953a58..d7c6149 100644
--- a/session_limit.install
+++ b/session_limit.install
@@ -12,7 +12,20 @@
  */
 function session_limit_uninstall() {
   variable_del('session_limit_max');
-  variable_del('session_limit_auto_drop');
+  variable_del('session_limit_behaviour');
   variable_del('session_limit_masquerade_ignore');
   db_query('DELETE FROM {variable} WHERE name LIKE "session_limit_rid_%"');
 }
+
+/**
+ * Implementation of hook_update_N().
+ */
+function session_limit_update_6200() {
+  if (variable_get('session_limit_auto_drop', 0)) {
+    drupal_load('module', 'session_limit');
+    variable_set('session_limit_behaviour', SESSION_LIMIT_DROP);
+  }
+  variable_del('session_limit_auto_drop');
+
+  return array();
+}
diff --git a/session_limit.module b/session_limit.module
index 23b2222..c3e87fc 100644
--- a/session_limit.module
+++ b/session_limit.module
@@ -6,6 +6,21 @@
  */
 
 /**
+ * Do nothing if the session limit is exceeded.
+ */
+define('SESSION_LIMIT_DO_NOTHING', 0);
+
+/**
+ * Automatically drop sessions that would exceed the limit.
+ */
+define('SESSION_LIMIT_DROP', 1);
+
+/**
+ * Disallow sessions that would exceed the limit.
+ */
+define('SESSION_LIMIT_DISALLOW_NEW', 2);
+
+/**
  * Implementation of hook_help().
  */
 function session_limit_help($path, $args) {
@@ -99,10 +114,16 @@ function session_limit_settings() {
     '#maxlength' => 3,
     '#description' => t('The maximum number of active sessions a user can have. 0 implies unlimited sessions.')
   );
-  $form['session_limit_auto_drop'] = array(
-    '#type' => 'checkbox',
-    '#title' => t('Automatically drop the oldest sessions without prompting.'),
-    '#default_value' => variable_get('session_limit_auto_drop', 0)
+  $limit_behaviours = array(
+    SESSION_LIMIT_DO_NOTHING => t('Do nothing.'),
+    SESSION_LIMIT_DROP => t('Automatically drop the oldest sessions without prompting.'),
+    SESSION_LIMIT_DISALLOW_NEW => t('Prevent new session.'),
+  );
+  $form['session_limit_behaviour'] = array(
+    '#type' => 'radios',
+    '#title' => t('When the session limit is exceeded'),
+    '#default_value' => variable_get('session_limit_behaviour', SESSION_LIMIT_DO_NOTHING),
+    '#options' => $limit_behaviours,
   );
   if (module_exists('masquerade')) {
     $form['session_limit_masquerade_ignore'] = array(
@@ -311,7 +332,7 @@ function session_limit_user_settings_submit($form, &$form_state) {
 function session_limit_page() {
   global $user;
 
-  if (variable_get('session_limit_auto_drop', 0)) {
+  if (variable_get('session_limit_behaviour', SESSION_LIMIT_DO_NOTHING) == SESSION_LIMIT_DROP) {
     // Get the oldest sessions.
     $count = db_result(db_query("SELECT COUNT(sid) FROM {sessions} WHERE uid = %d", $user->uid));
     $max_sessions = $count - session_limit_user_max_sessions($user);
@@ -323,6 +344,12 @@ function session_limit_page() {
 
     drupal_goto();
   }
+  else if (variable_get('session_limit_behaviour', SESSION_LIMIT_DO_NOTHING) == SESSION_LIMIT_DISALLOW_NEW) {
+    session_destroy();
+    $user = drupal_anonymous_user();
+
+    return;
+  }
 
   $result = db_query('SELECT * FROM {sessions} WHERE uid = %d', $user->uid);
   while ($obj =  db_fetch_object($result)) {