diff -u b/entityreference.install b/entityreference.install
--- b/entityreference.install
+++ b/entityreference.install
@@ -169,6 +169,10 @@
  */
 function entityreference_update_7100() {
   if (db_table_exists('taxonomy_index')) {
+    if (db_table_exists('taxonomy_index_tmp')) {
+      db_drop_table('taxonomy_index_tmp');
+    }
+
     $tx_schema = drupal_get_schema('taxonomy_index');
     db_create_table('taxonomy_index_tmp', $tx_schema);
     $select = db_select('taxonomy_index', 'tx');