diff --git a/lib/taskjuggler/ResourceScenario.rb b/lib/taskjuggler/ResourceScenario.rb
index b45e749e..0285bfc5 100644
--- a/lib/taskjuggler/ResourceScenario.rb
+++ b/lib/taskjuggler/ResourceScenario.rb
@@ -913,6 +913,14 @@ def countSlots(startIdx, endIdx)
       slots
     end
 
+    def countOnShiftSlots(startIdx, endIdx)
+      slots = 0
+      startIdx.upto(endIdx - 1) do |idx|
+        slots += 1 if onShift?(idx)
+      end
+      slots
+    end
+
     # Limit the _startIdx_ and _endIdx_ to the actually assigned interval.
     # If _task_ is provided, fit it for the bookings of this particular task.
     def fitIndicies(startIdx, endIdx, task = nil)
diff --git a/lib/taskjuggler/TimeSheets.rb b/lib/taskjuggler/TimeSheets.rb
index 91ecd699..13b764cf 100644
--- a/lib/taskjuggler/TimeSheets.rb
+++ b/lib/taskjuggler/TimeSheets.rb
@@ -291,13 +291,13 @@ def check
         # reported work.
         delta = 1
         if totalSlots < (targetSlots - delta)
-          error('ts_work_too_low',
+          warning('ts_work_too_low',
                 "The total work to be reported for this time sheet " +
                 "is #{workWithUnit(targetSlots)} but only " +
                 "#{workWithUnit(totalSlots)} were reported.")
         end
         if totalSlots > (targetSlots + delta)
-          error('ts_work_too_high',
+          warning('ts_work_too_high',
                 "The total work to be reported for this time sheet " +
                 "is #{workWithUnit(targetSlots)} but " +
                 "#{workWithUnit(totalSlots)} were reported.")
@@ -337,8 +337,9 @@ def totalNetWorkingSlots
       project = @resource.project
       startIdx = project.dateToIdx(@interval.start)
       endIdx = project.dateToIdx(@interval.end)
-      @resource.getAllocatedSlots(@scenarioIdx, startIdx, endIdx, nil) +
-        @resource.getFreeSlots(@scenarioIdx, startIdx, endIdx)
+      shiftSlots = @resource.countOnShiftSlots(@scenarioIdx, startIdx, endIdx)
+      allocatedSlots = @resource.getAllocatedSlots(@scenarioIdx, startIdx, endIdx, nil)
+      [shiftSlots,allocatedSlots].max
     end
 
     # Converts allocation percentage into time slots.