diff --git a/htdocs/categories/index.php b/htdocs/categories/index.php
index 29d8f9307f5..7e8d24db273 100644
--- a/htdocs/categories/index.php
+++ b/htdocs/categories/index.php
@@ -119,7 +119,7 @@ if ($conf->use_javascript)
 		print '<a href="'.$_SERVER["PHP_SELF"].'?expand=all">'.$langs->trans("ExpandAll").'</a>';
 		print '</td><td width="18"><img border="0" src="'.DOL_URL_ROOT.'/includes/treemenu/images/folder-expanded.gif">';
 	}
-	if ($_GET["expand"] != 'none')
+	if ($_GET["expand"] && $_GET["expand"] != 'none')
 	{
 		print '<a href="'.$_SERVER["PHP_SELF"].'?expand=none">'.$langs->trans("UndoExpandAll").'</a>';
 		print '</td><td width="18"><img border="0" src="'.DOL_URL_ROOT.'/includes/treemenu/images/folder.gif">';
diff --git a/htdocs/langs/en_US/main.lang b/htdocs/langs/en_US/main.lang
index 1088bc9a297..9850cef25dd 100644
--- a/htdocs/langs/en_US/main.lang
+++ b/htdocs/langs/en_US/main.lang
@@ -325,6 +325,10 @@ ShowAccountancyPreview=Show accountancy preview
 RefCustomer=Ref. customer
 Currency=Currency
 InfoAdmin=Information for administrators
+Undo=Undo
+Redo=Redo
+ExpandAll=Expand all
+UndoExpandAll=Undo expand
 # Countries
 CountryFR=France
 CountryBE=Belgium
diff --git a/htdocs/langs/fr_FR/main.lang b/htdocs/langs/fr_FR/main.lang
index b25c7bbefac..ab9877ba4c8 100644
--- a/htdocs/langs/fr_FR/main.lang
+++ b/htdocs/langs/fr_FR/main.lang
@@ -325,6 +325,10 @@ ShowAccountancyPreview=Afficher aper
 RefCustomer=Réf. client
 Currency=Devise
 InfoAdmin=Information pour les administrateurs
+Undo=Annuler
+Redo=Refaire
+ExpandAll=Tout dérouler
+UndoExpandAll=Annuler déroulement
 # Countries
 CountryFR=France
 CountryBE=Belgique