ha_innodb.cc:

  In TRUNCATE TABLE, MySQL may call innobase_xa_prepare() even though there is no active transaction because it was committed in ha_innobase::delete_all_rows(); in innobase_xa_prepare() InnoDB starts then a new transaction; let us adjust the trx->active_trans flag accordingly

sql/ha_innodb.cc

@@ -6313,6 +6313,14 @@ innobase_xa_prepare(
                 /* We were instructed to prepare the whole transaction, or
                 this is an SQL statement end and autocommit is on */
 
+		/* If there is no active InnoDB transaction,
+		trx_prepare_for_mysql() will (temporarily) start one */
+	
+        	if (trx->active_trans == 0) {
+
+                	trx->active_trans = 1;
+        	}
+
 		error = trx_prepare_for_mysql(trx);
 	} else {
 	        /* We just mark the SQL statement ended and do not do a