diff --git a/participate.py b/participate.py
index cfcca40..8420b32 100755
--- a/participate.py
+++ b/participate.py
@@ -566,6 +566,18 @@ def save_staff_slot(turn_id, slot_id, user_id):
       return True
   return False
 
+def check_user_availability(turn_id, user_id):
+  """ Check if user is available for this turn """
+  turn_start, turn_end = Tetawebapp_turns.query.filter(Tetawebapp_turns.id==turn_id).with_entities(Tetawebapp_turns.start_time, Tetawebapp_turns.end_time).first()
+  user_turns = Tetawebapp_staffs.query.filter(Tetawebapp_staffs.user_id==user_id).with_entities(Tetawebapp_staffs.turn_id).all()
+  for turn in user_turns:
+    t_start, t_end = Tetawebapp_staffs.query.filter(Tetawebapp_turns.id==turn[0]).with_entities(Tetawebapp_turns.start_time, Tetawebapp_turns.end_time).first()
+    if t_start <= turn_start and t_end > turn_start:
+        return False
+    if t_start >= turn_start and t_start < turn_end:
+      return False
+  return True
+
 ########################################################################
 # Role
 ########################################################################
@@ -943,8 +955,9 @@ def update_staff_slot(TURN_ID, SLOT_ID):
     user_id = session['user_id']
     user_name = get_user_name(user_id)
     if user_name != None:
-      if (save_staff_slot(turn_id, slot_id, user_id)):
-        return user_name
+      if check_user_availability(turn_id, user_id):
+        if (save_staff_slot(turn_id, slot_id, user_id)):
+          return user_name
     return "KO"
   except AttributeError as e:
     # User is not logged in