diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_curve.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_curve.py
index db493a3311..feebdf2601 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_curve.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/_add_segment_to_curve.py
@@ -128,10 +128,6 @@ def _add_segment_to_curve(file: ifcopenshell.file, segment: entity_instance, cur
     elif segment.DesignParameters.is_a("IfcAlignmentCantSegment") and not curve.is_a("IfcSegmentedReferenceCurve"):
         raise TypeError(f"Expected to see IfcSegmentedReferenceCurve, instead received '{curve.is_a()}'.")
 
-    expected_type = "IfcCompositeCurve"
-    if not curve.is_a(expected_type):
-        raise TypeError(f"Expected to see {expected_type}, instead received {curve.is_a()}.")
-
     # map the IfcAlignmentSegment to an IfcCurveSegment (or two in the case of helmert curves)
     if segment.DesignParameters.is_a("IfcAlignmentHorizontalSegment"):
         mapped_segments = _map_alignment_horizontal_segment(file, segment)
diff --git a/src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py b/src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py
index 96c3a9c1f2..a64eee9437 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/alignment/add_zero_length_segment.py
@@ -123,7 +123,8 @@ def add_zero_length_segment(file: ifcopenshell.file, layout: entity_instance, in
         if layout.is_a("IfcSegmentedReferenceCurve"):
             ifcopenshell.api.alignment.add_zero_length_segment(file, layout.BaseCurve)
         elif layout.is_a("IfcGradientCurve"):
-            ifcopenshell.api.alignment.add_zero_length_segment(file, layout.BaseCurve)
+            if layout.BaseCurve is not None:
+                ifcopenshell.api.alignment.add_zero_length_segment(file, layout.BaseCurve)
 
     else:
         zero_length_curve_segment = None