diff --git a/admin_menu.install b/admin_menu.install
index 61f3b7c..c5d1baf 100644
--- a/admin_menu.install
+++ b/admin_menu.install
@@ -97,3 +97,20 @@ function admin_menu_update_7303() {
     ->execute();
 }
 
+/**
+ * Remove obsolete 'admin_menu' menu and all orphan links in it.
+ */
+function admin_menu_update_7304() {
+  // 6.x-1.x cloned the entire link structure below the path 'admin' into a
+  // separate 'menu_name' "admin_menu" with 'module' "admin_menu". 6.x-3.x and
+  // early alpha versions of 7.x-3.x still did something similar. All of these
+  // records are obsolete. Removal of the 'module' records (without different
+  // menu_name) is particularly important, since they would otherwise appear
+  // as duplicate links.
+  db_delete('menu_links')
+    ->condition(db_or()
+      ->condition('module', 'admin_menu')
+      ->condition('menu_name', 'admin_menu')
+    )
+    ->execute();
+}