diff --git a/CRM/DataprocessorOutputExport/PDF.php b/CRM/DataprocessorOutputExport/PDF.php
index 3b091d5895a89929217c923da2242f7bbfd12d4f..cd35694e662b133a236ac50424ca50951ac86196 100644
--- a/CRM/DataprocessorOutputExport/PDF.php
+++ b/CRM/DataprocessorOutputExport/PDF.php
@@ -418,7 +418,7 @@ class CRM_DataprocessorOutputExport_PDF extends CRM_DataprocessorOutputExport_Ab
       fclose($file);
 
       if (isset($content['header'])) {
-        $file = fopen($filename.".html.header_part.".$sectionHeader, 'a');
+        $file = fopen($filename.".html.header_part.".$sectionHeader, 'w');
         fwrite($file, $content['header'] . "\r\n");
         fclose($file);
       }