diff --git a/metatags_quick.install b/metatags_quick.install
index 71f2821..e62c0ab 100644
--- a/metatags_quick.install
+++ b/metatags_quick.install
@@ -30,7 +30,10 @@ function metatags_quick_schema() {
         'description' => 'Language code',
       ),
     ),
-    'primary key' => array('id', 'path', 'lang',),
+    'primary key' => array('id'),
+    'unique keys' => array(
+      'lang_path' => array('lang', 'path'),
+    ),
   );
   return $schema;
 }
@@ -99,4 +102,22 @@ function metatags_quick_update_7003() {
     db_drop_field('metatags_quick_path_based', 'fid');
     db_drop_field('metatags_quick_path_based', 'value');
   }
-}
\ No newline at end of file
+}
+
+/**
+ * Change primary key to id field and add unique index on path and lang.
+ */
+function metatags_quick_update_7004() {
+  /*
+   * Normally we'd use db_drop_primary_key()/db_add_primary_key(), but MySQL
+   * wont let us drop the primary key if it's an autoincrement field. Altering
+   * like this, however, works.
+   *
+   * This will fail on SQLite, as its ALTER TABLE is rather simplified, but as
+   * this change is introduced because of SQLites failure to install in the
+   * first place, that's irrelevant. PostgreSQL seems to support the same
+   * syntax, so it should work.
+   */
+  db_query('ALTER TABLE {metatags_quick_path_based} DROP PRIMARY KEY, ADD PRIMARY KEY (`id`)');
+  db_add_unique_key('metatags_quick_path_based', 'lang_path', array('lang', 'path'));
+}