diff --git a/addons/resource/resource.py b/addons/resource/resource.py
index 73a6e2a3ec8..a37d8ca89fe 100644
--- a/addons/resource/resource.py
+++ b/addons/resource/resource.py
@@ -128,7 +128,8 @@ class resource_calendar(osv.osv):
                         d2 = datetime(dt_from.year, dt_from.month, dt_from.day, int(math.floor(m)), int((m%1) * 60))
                         result.append((d1, d2))
                         current_hour = hour_from
-                        todo -= (m-hour_from)
+                        # avoid float point error with round
+                        todo = round(todo - (hour_to - m), 4)
             dt_from -= timedelta(days=1)
             current_hour = 24
             maxrecur -= 1
@@ -180,7 +181,8 @@ class resource_calendar(osv.osv):
                             d2 = datetime(dt_from.year, dt_from.month, dt_from.day, int(math.floor(hour_to)), int((hour_to%1) * 60))
                             result.append((d1, d2))
                             current_hour = hour_to
-                            todo -= (hour_to - m)
+                            # avoid float point error with round
+                            todo = round(todo - (hour_to - m), 4)
                 dt_from += timedelta(days=1)
                 current_hour = 0
                 maxrecur -= 1