diff --git a/src/ifcopenshell-python/ifcopenshell/api/pset/edit_pset.py b/src/ifcopenshell-python/ifcopenshell/api/pset/edit_pset.py
index ff27ecfba4..a97c6a26ee 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/pset/edit_pset.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/pset/edit_pset.py
@@ -359,11 +359,17 @@ class Usecase:
             self.settings["pset"].Properties = props
 
     def get_properties(self):
+        """
+        Returns list of existing properties
+        """
         if hasattr(self.settings["pset"], "HasProperties"):
             return self.settings["pset"].HasProperties or []
+
         elif hasattr(self.settings["pset"], "Properties"):  # For IfcMaterialProperties
             return self.settings["pset"].Properties or []
 
+        raise TypeError(f"'{self.settings['pset']}' is not a valid pset")
+
     def get_primary_measure_type(self, name, old_value=None, new_value=None):
         if self.pset_template:
             for prop_template in self.pset_template.HasPropertyTemplates: