diff --git a/htdocs/lib/functions.inc.php b/htdocs/lib/functions.inc.php
index e03e1bc4017..8aa3f74904e 100644
--- a/htdocs/lib/functions.inc.php
+++ b/htdocs/lib/functions.inc.php
@@ -329,9 +329,9 @@ function print_liste_field_titre($name, $file, $field, $begin="", $options="")
 
   print $name." ";
   print '<a href="'.$file.'?sortfield='.$field.'&amp;sortorder=asc&begin='.$begin.$options.'">';
-  print '<img src="'.DOL_URL_ROOT.'/theme/'.$conf->theme.'/img/1downarrow.png" border="0"></a>';
+  print '<img src="'.DOL_URL_ROOT.'/theme/'.$conf->theme.'/img/1downarrow.png" border="0" alt="A-Z"></a>';
   print '<a href="'.$file.'?sortfield='.$field.'&amp;sortorder=desc&begin='.$begin.$options.'">';
-  print '<img src="'.DOL_URL_ROOT.'/theme/'.$conf->theme.'/img/1uparrow.png" border="0"></a>';
+  print '<img src="'.DOL_URL_ROOT.'/theme/'.$conf->theme.'/img/1uparrow.png" border="0" alt="Z-A"></a>';
 }
 
 function print_liste_field_titre_new($name, $file, $field, $begin="", $options="", $td="", $sortfield="")
@@ -352,9 +352,9 @@ function print_liste_field_titre_new($name, $file, $field, $begin="", $options="
     }
   print $name."&nbsp;";
   print '<a href="'.$file.'?sortfield='.$field.'&amp;sortorder=asc&begin='.$begin.$options.'">';
-  print '<img src="'.DOL_URL_ROOT.'/theme/'.$conf->theme.'/img/1downarrow.png" border="0"></a>';
+  print '<img src="'.DOL_URL_ROOT.'/theme/'.$conf->theme.'/img/1downarrow.png" border="0" alt="A-Z"></a>';
   print '<a href="'.$file.'?sortfield='.$field.'&amp;sortorder=desc&begin='.$begin.$options.'">';
-  print '<img src="'.DOL_URL_ROOT.'/theme/'.$conf->theme.'/img/1uparrow.png" border="0"></a>';
+  print '<img src="'.DOL_URL_ROOT.'/theme/'.$conf->theme.'/img/1uparrow.png" border="0" alt="Z-A"></a>';
   print "</td>";
 }