diff --git a/Classes/PHPExcel.php b/Classes/PHPExcel.php
index cc70286..ab3396b 100644
--- a/Classes/PHPExcel.php
+++ b/Classes/PHPExcel.php
@@ -607,6 +607,17 @@ class PHPExcel
 		return false;
 	}
 
+	/**
+	 * Check if style exists in style collection
+	 *
+	 * @param PHPExcel_Style $style
+	 * @return boolean
+	 */
+	public function cellXfExists($pCellStyle = null)
+	{
+		return in_array($pCellStyle, $this->_cellXfCollection, true);
+	}
+
 	/**
 	 * Get default style
 	 *
diff --git a/Classes/PHPExcel/Worksheet.php b/Classes/PHPExcel/Worksheet.php
index bc58a69..4ffd94f 100644
--- a/Classes/PHPExcel/Worksheet.php
+++ b/Classes/PHPExcel/Worksheet.php
@@ -1454,9 +1454,9 @@ class PHPExcel_Worksheet implements PHPExcel_IComparable
 
 		// Add the style to the workbook if necessary
 		$workbook = $this->_parent;
-		if ($existingStyle = $this->_parent->getCellXfByHashCode($pCellStyle->getHashCode())) {
-			// there is already such cell Xf in our collection
-			$xfIndex = $existingStyle->getIndex();
+		if ($this->_parent->cellXfExists($pCellStyle)) {
+			// there is already this cell Xf in our collection
+			$xfIndex = $pCellStyle->getIndex();
 		} else {
 			// we don't have such a cell Xf, need to add
 			$workbook->addCellXf($pCellStyle);
diff --git a/Examples/40duplicateStyle.php b/Examples/40duplicateStyle.php
new file mode 100644
index 0000000..52891ad
--- /dev/null
+++ b/Examples/40duplicateStyle.php
@@ -0,0 +1,51 @@
+<?php
+/** Error reporting */
+error_reporting(E_ALL);
+ini_set('display_errors', TRUE);
+ini_set('display_startup_errors', TRUE);
+date_default_timezone_set('Europe/London');
+
+define('EOL',(PHP_SAPI == 'cli') ? PHP_EOL : '<br />');
+
+date_default_timezone_set('Europe/London');
+
+/** Include PHPExcel */
+require_once '../Classes/PHPExcel.php';
+
+echo date('H:i:s') , " Create new PHPExcel object" , EOL;
+$objPHPExcel = new PHPExcel();
+$worksheet = $objPHPExcel->getActiveSheet();
+
+echo date('H:i:s') , " Create styles array" , EOL;
+$styles = array();
+for ($i = 0; $i < 10; $i++) {
+    $style = new PHPExcel_Style();
+    $style->getFont()->setSize($i + 4);
+    $styles[] = $style;
+}
+
+echo date('H:i:s') , " Add data (begin)" , EOL;
+$t = microtime(true);
+for ($col = 0; $col < 50; $col++) {
+    for ($row = 0; $row < 100; $row++) {
+        $str = ($row + $col);
+        $style = $styles[$row % 10];
+        $coord = PHPExcel_Cell::stringFromColumnIndex($col) . ($row + 1);
+        $worksheet->setCellValue($coord, $str);
+        $worksheet->duplicateStyle($style, $coord);
+    }
+}
+$d = microtime(true) - $t;
+echo date('H:i:s') , " Add data (end), time: " . round($d, 2) . " s", EOL;
+
+
+echo date('H:i:s') , " Write to Excel2007 format" , EOL;
+$objWriter = PHPExcel_IOFactory::createWriter($objPHPExcel, 'Excel2007');
+$objWriter->save(str_replace('.php', '.xlsx', __FILE__));
+echo date('H:i:s') , " File written to " , str_replace('.php', '.xlsx', pathinfo(__FILE__, PATHINFO_BASENAME)) , EOL;
+
+
+echo date('H:i:s') , " Peak memory usage: " , (memory_get_peak_usage(true) / 1024 / 1024) , " MB" , EOL;
+
+echo date('H:i:s') , " Done writing file" , EOL;
+echo 'File has been created in ' , getcwd() , EOL;