diff --git a/src/ifcopenshell-python/ifcopenshell/api/pset/edit_pset.py b/src/ifcopenshell-python/ifcopenshell/api/pset/edit_pset.py
index 58a453e774..81b57db874 100644
--- a/src/ifcopenshell-python/ifcopenshell/api/pset/edit_pset.py
+++ b/src/ifcopenshell-python/ifcopenshell/api/pset/edit_pset.py
@@ -278,7 +278,7 @@ class Usecase:
     def add_new_properties(self):
         properties = []
         for name, value in self.settings["properties"].items():
-            if value is None:
+            if value is None and self.settings["should_purge"]:
                 continue
             unit, value = self.unpack_unit_value(value)
 
@@ -343,8 +343,11 @@ class Usecase:
 
             else:
                 primary_measure_type = self.get_primary_measure_type(name, new_value=value)
-                value = self.cast_value_to_primary_measure_type(value, primary_measure_type)
-                nominal_value = self.file.create_entity(primary_measure_type, value)
+                if value is None:
+                    nominal_value = value
+                else:
+                    value = self.cast_value_to_primary_measure_type(value, primary_measure_type)
+                    nominal_value = self.file.create_entity(primary_measure_type, value)
                 args = {"Name": name, "NominalValue": nominal_value}
                 if unit:
                     args["Unit"] = unit
diff --git a/src/ifcopenshell-python/test/api/pset/test_edit_pset.py b/src/ifcopenshell-python/test/api/pset/test_edit_pset.py
index d7c8fdf025..d7c0db240e 100644
--- a/src/ifcopenshell-python/test/api/pset/test_edit_pset.py
+++ b/src/ifcopenshell-python/test/api/pset/test_edit_pset.py
@@ -84,11 +84,19 @@ class TestEditPset(test.bootstrap.IFC4):
         assert pset.HasProperties[0].NominalValue.is_a("IfcThermalTransmittanceMeasure")
         assert pset.HasProperties[0].NominalValue.wrappedValue == 42
 
-    def test_not_adding_a_property_if_it_is_none(self):
+    def test_adding_a_property_if_it_is_none(self):
         element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
         pset = ifcopenshell.api.run("pset.add_pset", self.file, product=element, name="Pset_WallCommon")
+        # should_purge is false by default
         ifcopenshell.api.run("pset.edit_pset", self.file, pset=pset, properties={"Reference": None})
         pset = element.IsDefinedBy[0].RelatingPropertyDefinition
+        assert len(pset.HasProperties) == 1
+
+    def test_not_adding_a_property_if_it_is_none_and_should_purge_is_true(self):
+        element = ifcopenshell.api.run("root.create_entity", self.file, ifc_class="IfcWall")
+        pset = ifcopenshell.api.run("pset.add_pset", self.file, product=element, name="Pset_WallCommon")
+        ifcopenshell.api.run("pset.edit_pset", self.file, pset=pset, properties={"Reference": None}, should_purge=True)
+        pset = element.IsDefinedBy[0].RelatingPropertyDefinition
         assert len(pset.HasProperties) == 0
 
     def test_removing_a_none_property_if_specified(self):