diff --git a/src/ifcopenshell-python/ifcopenshell/api/sequence/cascade_schedule.py b/src/ifcopenshell-python/ifcopenshell/api/sequence/cascade_schedule.py
index b541a81670..5285cf201e 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/sequence/cascade_schedule.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/sequence/cascade_schedule.py
@@ -153,7 +153,8 @@ class Usecase:
                 days = 0 if predecessor_duration.days == 0 else 1
                 duration_type = "WORKTIME"
                 if rel.TimeLag:
-                    days += self.get_lag_time_days(rel.TimeLag)
+                    # updated to handle IfcRatioMeasure as a TimeLag value
+                    days += self.get_lag_time_days(rel.TimeLag) if rel.TimeLag.is_a("IfcDuration") else predecessor_duration.days * rel.TimeLag.LagValue.wrappedValue
                     duration_type = rel.TimeLag.DurationType
                 if days:
                     starts.append(
@@ -182,7 +183,7 @@ class Usecase:
                 if not start:
                     continue
                 if rel.TimeLag:
-                    days = self.get_lag_time_days(rel.TimeLag)
+                    days = self.get_lag_time_days(rel.TimeLag) if rel.TimeLag.is_a("IfcDuration") else predecessor_duration.days * rel.TimeLag.LagValue.wrappedValue
                     duration_type = rel.TimeLag.DurationType
                     starts.append(
                         self.offset_date(
@@ -201,7 +202,7 @@ class Usecase:
                 if not finish:
                     continue
                 if rel.TimeLag:
-                    days = self.get_lag_time_days(rel.TimeLag)
+                    days = self.get_lag_time_days(rel.TimeLag) if rel.TimeLag.is_a("IfcDuration") else predecessor_duration.days * rel.TimeLag.LagValue.wrappedValue
                     duration_type = rel.TimeLag.DurationType
                     finishes.append(
                         self.offset_date(
@@ -222,7 +223,7 @@ class Usecase:
                 days = -1
                 duration_type = "WORKTIME"
                 if rel.TimeLag:
-                    days += self.get_lag_time_days(rel.TimeLag)
+                    days += self.get_lag_time_days(rel.TimeLag) if rel.TimeLag.is_a("IfcDuration") else predecessor_duration.days * rel.TimeLag.LagValue.wrappedValue
                     duration_type = rel.TimeLag.DurationType
                 if days or rel.TimeLag:
                     finishes.append(