diff --git a/entityreference.install b/entityreference.install
index e6d1b0d..51e4279 100644
--- a/entityreference.install
+++ b/entityreference.install
@@ -155,5 +155,10 @@ function entityreference_update_7001() {
     db_drop_field($revision_name, $field_name . '_target_type');
     db_drop_index($revision_name, $field_name . '_target_entity');
     db_add_index($revision_name, $field_name . '_target_id', array($field_name . '_target_id'));
+
+    // Update the field settings.
+    $field = field_info_field($field_name);
+    $field['indexes'] = array('target_id' => array('target_id'));
+    field_update_field($field);
   }
 }