diff --git a/kfet/templates/kfet/kpsul.html b/kfet/templates/kfet/kpsul.html
index 2d7a1238..8b8a335a 100644
--- a/kfet/templates/kfet/kpsul.html
+++ b/kfet/templates/kfet/kpsul.html
@@ -378,6 +378,14 @@ $(document).ready(function() {
         }
         if ('negative' in data['errors'])
             content += '<a class="btn btn-primary" href="/k-fet/accounts/'+account_data['trigramme']+'/edit" target="_blank">Autorisation de négatif requise</a>';
+        if ('addcost' in data['errors']) {
+            content += '<ul>';
+            if (data['errors']['addcost'].indexOf('__all__') != -1)
+                content += '<li>Compte invalide</li>';
+            if (data['errors']['addcost'].indexOf('amount') != -1)
+                content += '<li>Montant invalide</li>';
+            content += '</ul>';
+        }
         return content;
     }
 
@@ -1082,16 +1090,16 @@ $(document).ready(function() {
                     });
                     break;
                 case 400:
-                    displayErrors(getErrorsHtml(data));
+                    askAddcost(getErrorsHtml(data));
                     break;
             }
         });
     }
 
-    function askAddcost() {
+    function askAddcost(errors = '') {
         $.confirm({
             title: 'Majoration',
-            content: '<input type="text" placeholder="Trigramme" autocomplete="off" name="trigramme" spellcheck="false" style="text-transform:uppercase" autofocus><input type="number" step="0.01" min="0.01" placeholder="€" name="amount">',
+            content: errors + '<input type="text" placeholder="Trigramme" autocomplete="off" name="trigramme" spellcheck="false" style="text-transform:uppercase" autofocus><input type="number" step="0.01" min="0.01" placeholder="€" name="amount">',
             backgroundDismiss: true,
             animation:'top',
             closeAnimation:'bottom',
@@ -1108,7 +1116,7 @@ $(document).ready(function() {
                         that.$confirmButton.click();
                 });
             },
-            onClose: function() { this._lastFocused = articleSelect; }
+            onClose: function() { this._lastFocused = triInput; }
         });
     }
 
diff --git a/kfet/views.py b/kfet/views.py
index 4702f614..7e5f38d3 100644
--- a/kfet/views.py
+++ b/kfet/views.py
@@ -535,8 +535,8 @@ def kpsul_update_addcost(request):
     addcost_form = AddcostForm(request.POST)
 
     if not addcost_form.is_valid():
-        print(addcost_form.errors)
-        return JsonResponse({}, status=400)
+        data = { 'errors': { 'addcost': list(addcost_form.errors) } }
+        return JsonResponse(data, status=400)
     required_perms = ['kfet.manage_addcosts']
     if not request.user.has_perms(required_perms):
         data = {