diff --git a/htdocs/core/lib/functions.lib.php b/htdocs/core/lib/functions.lib.php
index 162e88a8e4b..e969a82a7a8 100644
--- a/htdocs/core/lib/functions.lib.php
+++ b/htdocs/core/lib/functions.lib.php
@@ -3423,6 +3423,8 @@ function price2num($amount,$rounding='',$alreadysqlnb=0)
  */
 function showDimensionInBestUnit($dimension, $unit, $type, $outputlangs, $round=-1)
 {
+    require_once DOL_DOCUMENT_ROOT.'/core/lib/product.lib.php';
+    
     if ($dimension < 1/10000) 
     {
         $dimension = $dimension * 1000000;