diff --git a/install-dev/classes/xmlLoader.php b/install-dev/classes/xmlLoader.php
index 80142bf7b..8528bc37c 100644
--- a/install-dev/classes/xmlLoader.php
+++ b/install-dev/classes/xmlLoader.php
@@ -683,7 +683,7 @@ class InstallXmlLoader
 		if (!isset($columns[$table]))
 		{
 			$columns[$table] = array();
-			$sql = 'SHOW COLUMNS FROM `'.bqSQL(_DB_PREFIX_.$table).'`';
+			$sql = 'SHOW COLUMNS FROM `'._DB_PREFIX_.bqSQL($table).'`';
 			foreach (Db::getInstance()->executeS($sql) as $row)
 				$columns[$table][$row['Field']] = $this->checkIfTypeIsText($row['Type']);
 		}
diff --git a/install-dev/models/install.php b/install-dev/models/install.php
index cb1d437f4..830429a13 100644
--- a/install-dev/models/install.php
+++ b/install-dev/models/install.php
@@ -131,8 +131,8 @@ class InstallModelInstall extends InstallAbstractModel
 		foreach (Db::getInstance()->executeS('SHOW TABLES') as $row)
 		{
 			$table = current($row);
-			if (preg_match('#^'._DB_PREFIX_.'#i', $table))
-				Db::getInstance()->execute((($truncate) ? 'TRUNCATE' : 'DROP TABLE').' '.$table);
+			if (!_DB_PREFIX_ || preg_match('#^'._DB_PREFIX_.'#i', $table))
+				Db::getInstance()->execute((($truncate) ? 'TRUNCATE' : 'DROP TABLE').' `'.$table.'`');
 		}
 	}