diff --git a/addons/mrp_operations/mrp_operations.py b/addons/mrp_operations/mrp_operations.py
index 52fdda1a7b2..b464f7045e6 100644
--- a/addons/mrp_operations/mrp_operations.py
+++ b/addons/mrp_operations/mrp_operations.py
@@ -279,7 +279,8 @@ class mrp_production(osv.osv):
                     i = self.pool.get('resource.calendar').interval_get(
                         cr,
                         uid,
-                        wc.workcenter_id.calendar_id and wc.workcenter_id.calendar_id.id or False,
+                        #passing False makes resource_resource._schedule_hours run 1000 iterations doing nothing
+                        wc.workcenter_id.calendar_id and wc.workcenter_id.calendar_id.id or None,
                         dt,
                         wc.hour or 0.0
                     )
diff --git a/addons/resource/resource.py b/addons/resource/resource.py
index 962cad9eb92..58acc0cd170 100644
--- a/addons/resource/resource.py
+++ b/addons/resource/resource.py
@@ -436,7 +436,7 @@ class resource_calendar(osv.osv):
 
             working_intervals = self.get_working_intervals_of_day(cr, uid, id, **call_args)
 
-            if id is None and not working_interval:  # no calendar -> consider working 8 hours
+            if id is None and not working_intervals:  # no calendar -> consider working 8 hours
                 remaining_hours -= 8.0
             elif working_intervals:
                 if backwards: