diff --git a/Classes/PHPExcel.php b/Classes/PHPExcel.php
index 5c66cf45..2a450c4c 100644
--- a/Classes/PHPExcel.php
+++ b/Classes/PHPExcel.php
@@ -133,6 +133,7 @@ class PHPExcel
      *
      */
     public function disconnectWorksheets() {
+    	$worksheet = NULL;
         foreach($this->_workSheetCollection as $k => &$worksheet) {
             $worksheet->disconnectCells();
             $this->_workSheetCollection[$k] = null;
@@ -141,6 +142,14 @@ class PHPExcel
         $this->_workSheetCollection = array();
     }
 
+    /**
+     * Code to execute when this worksheet is unset()
+     *
+     */
+	function __destruct() {
+		$this->disconnectWorksheets();
+	}
+
     /**
      * Get properties
      *
diff --git a/Classes/PHPExcel/Worksheet.php b/Classes/PHPExcel/Worksheet.php
index 2cdaca75..c8b70fe1 100644
--- a/Classes/PHPExcel/Worksheet.php
+++ b/Classes/PHPExcel/Worksheet.php
@@ -379,13 +379,23 @@ class PHPExcel_Worksheet implements PHPExcel_IComparable
     public function disconnectCells()
     {
         $this->_cellCollection->unsetWorksheetCells();
-        $this->_cellCollection = null;
+        $this->_cellCollection = NULL;
 
         //    detach ourself from the workbook, so that it can then delete this worksheet successfully
         $this->_parent = null;
     }
 
     /**
+     * Code to execute when this worksheet is unset()
+     *
+     */
+	function __destruct() {
+		if ($this->_cellCollection !== NULL) {
+			$this->disconnectCells();
+		}
+	}
+
+   /**
      * Return the cache controller for the cell collection
      *
      * @return PHPExcel_CachedObjectStorage_xxx