diff --git a/bin/addons/base/ir/workflow/print_instance.py b/bin/addons/base/ir/workflow/print_instance.py
index 7a12e5902d3..495c4a2f5a8 100644
--- a/bin/addons/base/ir/workflow/print_instance.py
+++ b/bin/addons/base/ir/workflow/print_instance.py
@@ -82,7 +82,10 @@ def graph_get(cr, graph, wkf_id, nested=False, workitem={}):
     start = cr.fetchone()[0]
     cr.execute("select 'subflow.'||name,id from wkf_activity where flow_stop=True and wkf_id=%s", (wkf_id,))
     stop = cr.fetchall()
-    stop = (stop[0][1], dict(stop))
+    if (stop):
+        stop = (stop[0][1], dict(stop))
+    else:
+        stop = ("stop",{})
     return ((start,{}),stop)
 
 
diff --git a/bin/workflow/instance.py b/bin/workflow/instance.py
index 99e041ab860..8f1c8455598 100644
--- a/bin/workflow/instance.py
+++ b/bin/workflow/instance.py
@@ -43,6 +43,7 @@ def delete(cr, ident):
 
 def validate(cr, inst_id, ident, signal, force_running=False):
     cr.execute("select * from wkf_workitem where inst_id=%s", (inst_id,))
+    stack = None
     for witem in cr.dictfetchall():
         stack = []
         workitem.process(cr, witem, ident, signal, force_running, stack=stack)