diff --git a/src/blenderbim/blenderbim/bim/module/geometry/operator.py b/src/blenderbim/blenderbim/bim/module/geometry/operator.py
index 21e998bc67..d3ddc4222f 100644
--- a/src/blenderbim/blenderbim/bim/module/geometry/operator.py
+++ b/src/blenderbim/blenderbim/bim/module/geometry/operator.py
@@ -272,7 +272,8 @@ class UpdateRepresentation(bpy.types.Operator, Operator):
             if self.ifc_representation_class == "IfcTessellatedFaceSet":
                 # We are explicitly casting to a tessellation, so remove all parametric materials.
                 element_type = ifcopenshell.util.element.get_type(product)
-                ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), product=element_type)
+                if element_type:  # Some invalid IFCs use material sets without a type.
+                    ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), product=element_type)
                 ifcopenshell.api.run("material.unassign_material", tool.Ifc.get(), product=product)
             else:
                 # These objects are parametrically based on an axis and should not be modified as a mesh