diff --git a/Classes/PHPExcel/Writer/Excel2007/Chart.php b/Classes/PHPExcel/Writer/Excel2007/Chart.php
index 35ca564..e5bf00d 100644
--- a/Classes/PHPExcel/Writer/Excel2007/Chart.php
+++ b/Classes/PHPExcel/Writer/Excel2007/Chart.php
@@ -940,9 +940,11 @@ class PHPExcel_Writer_Excel2007_Chart extends PHPExcel_Writer_Excel2007_WriterPa
 						($groupType != PHPExcel_Chart_DataSeries::TYPE_PIECHART_3D) &&
 						($groupType != PHPExcel_Chart_DataSeries::TYPE_DONUTCHART)) {
 
-						$objWriter->startElement('c:formatCode');
-							$objWriter->writeRawData( $plotSeriesValues->getFormatCode() );
-						$objWriter->endElement();
+						if ($plotSeriesValues->getFormatCode() !== NULL) {
+							$objWriter->startElement('c:formatCode');
+								$objWriter->writeRawData( $plotSeriesValues->getFormatCode() );
+							$objWriter->endElement();
+						}
 					}
 
 					$objWriter->startElement('c:ptCount');