diff --git a/simplesamlphp_auth.install b/simplesamlphp_auth.install
index 9174767..1861d39 100644
--- a/simplesamlphp_auth.install
+++ b/simplesamlphp_auth.install
@@ -45,5 +45,5 @@ function simplesamlphp_auth_uninstall() {
   variable_del('simplesamlphp_auth_allowdefaultloginroles');
   variable_del('simplesamlphp_auth_allowdefaultloginusers');
   variable_del('simplesamlphp_auth_logoutgotourl');
-
+  variable_del('simplesamlphp_auth_addauthmaps');
 }
diff --git a/simplesamlphp_auth.module b/simplesamlphp_auth.module
index 5c5f200..579ea48 100644
--- a/simplesamlphp_auth.module
+++ b/simplesamlphp_auth.module
@@ -232,9 +232,16 @@ function simplesamlphp_auth_init() {
         $ext_user = user_external_load($authname);
         $skip_user_finalization = FALSE;
 
+        // Add authmaps on the fly for manually created users.
+        if (!$ext_user && ($existing_user = user_load_by_name($authname)) && variable_get('simplesamlphp_auth_addauthmaps', TRUE)) {
+          user_set_authmaps($existing_user, array('simplesamlphp_auth' => $existing_user->name));
+          $ext_user = $existing_user;
+        }
+
         if (!$ext_user) {
           // First we check the admin settings for simpleSAMLphp and find out if we are allowed to register users.
-          if (variable_get('simplesamlphp_auth_registerusers', TRUE)) {
+          // If a user exists with this username, we don't register a new one.
+          if (variable_get('simplesamlphp_auth_registerusers', TRUE) && !$existing_user) {
 
             // We are allowed to register new users.
             _simplesaml_auth_debug(t('Register [%authname]', array('%authname' => $authname)));
@@ -537,7 +544,13 @@ function simplesamlphp_auth_settings() {
     '#type' => 'checkbox',
     '#title' => t('Register users (i.e., auto-provisioning)'),
     '#default_value' => variable_get('simplesamlphp_auth_registerusers', TRUE),
-    '#description' => t('Determines wether or not the module should automatically create/register new Drupal accounts for users that authenticate using SimpleSAMLphp. Unless you\'ve done some custom work to provision Drupal accounts with the necessary authmap entries you will want this checked.<br /><br />NOTE: If unchecked each user must already have been provisioned a Drupal account with an appropriate entry in the authmap table before logging in. Otherwise they will receive a notice and be denied access. Be aware that simply creating a Drupal account will not create the necessary entry in the authmap table.'),
+    '#description' => t('Determines wether or not the module should automatically create/register new Drupal accounts for users that authenticate using SimpleSAMLphp.'),
+  );
+  $form['simplesamlphp_auth_grp_reg']['simplesamlphp_auth_addauthmaps'] = array(
+    '#type' => 'checkbox',
+    '#title' => t('Enable authentication for manually created users'),
+    '#default_value' => variable_get('simplesamlphp_auth_addauthmaps', TRUE),
+    '#description' => t('Allows users accounts created manually (not created by auto-provisoning) to authenticate using SimpleSAMLphp by adding the necessary authmap entries.'),
   );
 
   $form['simplesamlphp_auth_grp_auth'] = array(