diff --git a/htdocs/includes/fpdf/DolibarrPdfBarCode.class.php b/htdocs/includes/fpdf/DolibarrPdfBarCode.class.php
index 37a55874f9d..f099420820c 100644
--- a/htdocs/includes/fpdf/DolibarrPdfBarCode.class.php
+++ b/htdocs/includes/fpdf/DolibarrPdfBarCode.class.php
@@ -20,6 +20,8 @@
  *
  */
 
+require_once(FPDF_PATH.'fpdf.php');
+
 class DolibarrPdfBarCode extends FPDF {
 
   /* Author Olivier PLATHEY
diff --git a/htdocs/includes/fpdf/code39ext/code39.php b/htdocs/includes/fpdf/code39ext/code39.php
index dd9e1a781fc..ed526d9414f 100755
--- a/htdocs/includes/fpdf/code39ext/code39.php
+++ b/htdocs/includes/fpdf/code39ext/code39.php
@@ -1,5 +1,5 @@
 <?php
-require('fpdf.php');
+require_once(FPDF_PATH.'fpdf.php');
 
 class PDF_Code39 extends FPDF {
 
diff --git a/htdocs/includes/fpdf/i25/i25.php b/htdocs/includes/fpdf/i25/i25.php
index 5ef1c006d82..60a971a3d60 100755
--- a/htdocs/includes/fpdf/i25/i25.php
+++ b/htdocs/includes/fpdf/i25/i25.php
@@ -1,5 +1,5 @@
 <?php
-require('fpdf.php');
+require_once(FPDF_PATH.'fpdf.php');
 
 // based on the Code 39 script from The-eh
 class PDF_i25 extends FPDF