diff --git a/modules/system/system.install b/modules/system/system.install
index 8661ac40eee66e10c6357447f4e6d90d93f94ec4..3245fc30323be6773d4947341b57b453bff45774 100644
--- a/modules/system/system.install
+++ b/modules/system/system.install
@@ -2046,6 +2046,7 @@ function system_update_7017() {
 function system_update_7018() {
   $ret = array();
   db_drop_index($ret, 'system', 'modules');
+  db_drop_index($ret, 'system', 'type_name');
   db_change_field($ret, 'system', 'type', 'type', array('type' => 'varchar', 'length' => 12, 'not null' => TRUE, 'default' => ''));
   db_add_index($ret, 'system', 'modules', array('type', 'status', 'weight', 'name'));
   db_add_index($ret, 'system', 'type_name', array('type', 'name'));