diff --git a/addons/web_diagram/controllers/main.py b/addons/web_diagram/controllers/main.py
index d9a435f1924..0e89eb13db2 100644
--- a/addons/web_diagram/controllers/main.py
+++ b/addons/web_diagram/controllers/main.py
@@ -48,7 +48,7 @@ class DiagramView(openerp.http.Controller):
         for tr in transitions:
             list_tr.append(tr)
             connectors.setdefault(tr, {
-                'id': tr,
+                'id': int(tr),
                 's_id': transitions[tr][0],
                 'd_id': transitions[tr][1]
             })