diff --git a/Classes/PHPExcel/Shared/OLE/PPS/Root.php b/Classes/PHPExcel/Shared/OLE/PPS/Root.php
index d06b14f..532e652 100644
--- a/Classes/PHPExcel/Shared/OLE/PPS/Root.php
+++ b/Classes/PHPExcel/Shared/OLE/PPS/Root.php
@@ -34,7 +34,7 @@ class PHPExcel_Shared_OLE_PPS_Root extends PHPExcel_Shared_OLE_PPS
 	 *	Directory for temporary files
 	 *	@var string
 	 */
-	protected $_tmp_dir		= '';
+	protected $_tmp_dir		= NULL;
 
 	/**
 	 * @param integer $time_1st A timestamp
@@ -79,6 +79,8 @@ class PHPExcel_Shared_OLE_PPS_Root extends PHPExcel_Shared_OLE_PPS
 		if (is_resource($filename)) {
 		    $this->_FILEH_ = $filename;
 		} else if ($filename == '-' || $filename == '') {
+			if (is_null($this->_tmp_dir))
+				$this->_tmp_dir = PHPExcel_Shared_File::sys_get_temp_dir();
 			$this->_tmp_filename = tempnam($this->_tmp_dir, "OLE_PPS_Root");
 			$this->_FILEH_ = fopen($this->_tmp_filename,"w+b");
 			if ($this->_FILEH_ == false) {
diff --git a/Classes/PHPExcel/Shared/XMLWriter.php b/Classes/PHPExcel/Shared/XMLWriter.php
index cc955d7..c7dfeb5 100644
--- a/Classes/PHPExcel/Shared/XMLWriter.php
+++ b/Classes/PHPExcel/Shared/XMLWriter.php
@@ -59,12 +59,14 @@ class PHPExcel_Shared_XMLWriter extends XMLWriter {
 	 * @param int		$pTemporaryStorage			Temporary storage location
 	 * @param string	$pTemporaryStorageFolder	Temporary storage folder
 	 */
-	public function __construct($pTemporaryStorage = self::STORAGE_MEMORY, $pTemporaryStorageFolder = './') {
+	public function __construct($pTemporaryStorage = self::STORAGE_MEMORY, $pTemporaryStorageFolder = NULL) {
 		// Open temporary storage
 		if ($pTemporaryStorage == self::STORAGE_MEMORY) {
 			$this->openMemory();
 		} else {
 			// Create temporary filename
+			if (is_null($pTemporaryStorageFolder))
+				$pTemporaryStorageFolder = PHPExcel_Shared_File::sys_get_temp_dir();
 			$this->_tempFileName = @tempnam($pTemporaryStorageFolder, 'xml');
 
 			// Open storage