diff --git a/templates/web/thesaurus/thesaurus.html.twig b/templates/web/thesaurus/thesaurus.html.twig
index 48b4492a0b..3a950ea27e 100644
--- a/templates/web/thesaurus/thesaurus.html.twig
+++ b/templates/web/thesaurus/thesaurus.html.twig
@@ -39,6 +39,14 @@
                 self.location.replace("thesaurus.php?piv={{ piv }}&bid={{ bid }}") ;
             }
 
+            function inputChanged() {
+                if ($("[name=term]").val().length > 0) {
+                    $("[name=term]").css('border-color', '');
+                } else {
+                    $("[name=term]").css('border-color', '#F00');
+                }
+            }
+
             function test(div)
             {
                 t = document.getElementById(div).innerHTML;
@@ -262,7 +270,7 @@
                         <tr>
                             <td style="text-align:right; width:80px;"><span class="label"></span> :&nbsp;</td>
                             <td></td>
-                            <td><input type="text" style="width:250px;" name="term"></td>
+                            <td><input type="text" style="width:250px;" name="term" onkeyup="inputChanged();return(false);"></td>
                         </tr>
                         <tr>
                             <td style="text-align:right">{{ 'thesaurus:: contexte'  | trans }} : </td>
@@ -976,6 +984,10 @@
                                                             var myObj = { "win":window };
 
                                                             var t = zdialog.find("[name=term]").val();
+                                                            if (t.length == 0) {
+                                                                zdialog.find("[name=term]").css('border-color', '#F00');
+                                                                return;
+                                                            }
                                                             var k = zdialog.find("[name=context]").val();
                                                             if(k != "") {
                                                                 t += " (" + k + ")";