diff --git a/src/ifc4d/ifc4d/csv4d2ifc.py b/src/ifc4d/ifc4d/csv4d2ifc.py
index 79f551fa47..a5f6a460a9 100644
--- a/src/ifc4d/ifc4d/csv4d2ifc.py
+++ b/src/ifc4d/ifc4d/csv4d2ifc.py
@@ -86,12 +86,12 @@ class Csv2Ifc:
 
         task_relationships = self.parse_task_rel(row[self.headers["Relationships"]])
 
-        scheduled_start_date = ifcopenshell.util.date.string_to_date(row[self.headers["ScheduleStart"]])
-        scheduled_finish_date = ifcopenshell.util.date.string_to_date(row[self.headers["ScheduleFinish"]])
-        scheduled_duration = ifcopenshell.util.date.string_to_duration(row[self.headers["ScheduleDuration"]])
-        actual_start_date = ifcopenshell.util.date.string_to_date(row[self.headers["ActualStart"]])
-        actual_finish_date = ifcopenshell.util.date.string_to_date(row[self.headers["ActualFinish"]])
-        actual_duration = ifcopenshell.util.date.string_to_duration(row[self.headers["ActualDuration"]])
+        scheduled_start_date = ifcopenshell.util.date.string_to_date(row[self.headers["ScheduleStart"]]) if row[self.headers["ScheduleStart"]] else None
+        scheduled_finish_date = ifcopenshell.util.date.string_to_date(row[self.headers["ScheduleFinish"]]) if row[self.headers["ScheduleFinish"]] else None
+        scheduled_duration = ifcopenshell.util.date.string_to_duration(row[self.headers["ScheduleDuration"]]) if row[self.headers["ScheduleDuration"]] else None
+        actual_start_date = ifcopenshell.util.date.string_to_date(row[self.headers["ActualStart"]]) if row[self.headers["ActualStart"]] else None
+        actual_finish_date = ifcopenshell.util.date.string_to_date(row[self.headers["ActualFinish"]]) if row[self.headers["ActualFinish"]] else None
+        actual_duration = ifcopenshell.util.date.string_to_duration(row[self.headers["ActualDuration"]]) if row[self.headers["ActualDuration"]] else None
 
         return {
             "Hierarchy": hierarchy,
@@ -162,7 +162,7 @@ class Csv2Ifc:
                 "ScheduleStart": task["ScheduleStart"],
                 "ScheduleFinish": task["ScheduleFinish"],
                 "DurationType": "WORKTIME" if task["ScheduleDuration"] else None,
-                "ScheduleDuration": task["ScheduleDuration"] if task["ScheduleDuration"] else None,
+                "ScheduleDuration": task["ScheduleDuration"],
                 "ActualStart": task["ActualStart"],
                 "ActualFinish": task["ActualFinish"],
                 "ActualDuration": task["ActualDuration"],