diff --git a/htdocs/core/lib/pdf.lib.php b/htdocs/core/lib/pdf.lib.php
index 9ce3819cc65..822fcdcd44b 100644
--- a/htdocs/core/lib/pdf.lib.php
+++ b/htdocs/core/lib/pdf.lib.php
@@ -1180,7 +1180,7 @@ function pdf_writelinedesc(&$pdf, $object, $i, $outputlangs, $w, $h, $posx, $pos
 	//if (is_object($hookmanager) && ( (isset($object->lines[$i]->product_type) && $object->lines[$i]->product_type == 9 && ! empty($object->lines[$i]->special_code)) || ! empty($object->lines[$i]->fk_parent_line) ) )
 	if (is_object($hookmanager))   // Old code is commented on preceding line. Reproduct this test in the pdf_xxx function if you don't want your hook to run
 	{
-		$special_code = $object->lines[$i]->special_code;
+		$special_code = empty($object->lines[$i]->special_code) ? '' : $object->lines[$i]->special_code;
 		if (!empty($object->lines[$i]->fk_parent_line)) $special_code = $object->getSpecialCode($object->lines[$i]->fk_parent_line);
 		$parameters = array('pdf'=>$pdf, 'i'=>$i, 'outputlangs'=>$outputlangs, 'w'=>$w, 'h'=>$h, 'posx'=>$posx, 'posy'=>$posy, 'hideref'=>$hideref, 'hidedesc'=>$hidedesc, 'issupplierline'=>$issupplierline, 'special_code'=>$special_code);
 		$action = '';