diff --git a/system/database/drivers/mysqli/mysqli_driver.php b/system/database/drivers/mysqli/mysqli_driver.php
index 74f55c4..4575824 100644
--- a/system/database/drivers/mysqli/mysqli_driver.php
+++ b/system/database/drivers/mysqli/mysqli_driver.php
@@ -54,6 +54,9 @@
 	 */
 	var $delete_hack = TRUE;
 
+	// whether SET NAMES must be used to set the character set
+	var $use_set_names;
+	
 	// --------------------------------------------------------------------
 
 	/**
@@ -132,15 +135,13 @@
 	 */
 	function _db_set_charset($charset, $collation)
 	{
-		static $use_set_names;
-
-		if ( ! isset($use_set_names))
+		if ( ! isset($this->use_set_names))
 		{
 			// mysqli_set_charset() requires MySQL >= 5.0.7, use SET NAMES as fallback
-			$use_set_names = (version_compare(mysqli_get_server_info($this->conn_id), '5.0.7', '>=')) ? FALSE : TRUE;
+			$this->use_set_names = (version_compare(mysqli_get_server_info($this->conn_id), '5.0.7', '>=')) ? FALSE : TRUE;
 		}
 
-		if ($use_set_names)
+		if ($this->use_set_names === TRUE)
 		{
 			return @mysqli_query($this->conn_id, "SET NAMES '".$this->escape_str($charset)."' COLLATE '".$this->escape_str($collation)."'");
 		}