diff --git a/work.py b/work.py
index f9ca0b91a6..e972c18bc9 100644
--- a/work.py
+++ b/work.py
@@ -110,14 +110,14 @@ class Work:
                     leafs.add(work.id)
 
                 total_allocation = 0
+                effort = work.effort_duration or datetime.timedelta()
                 if not work.allocations:
-                    durations[work.id] = (work.effort_duration
-                        or datetime.timedelta())
+                    durations[work.id] = effort
                     continue
                 for allocation in work.allocations:
                     total_allocation += allocation.percentage
                 durations[work.id] = datetime.timedelta(
-                    seconds=work.effort_duration.total_seconds()
+                    seconds=effort.total_seconds()
                     / (total_allocation / 100.0))
 
             while leafs: