diff --git a/src/materialsdb/ifc/material_psets.json b/src/materialsdb/ifc/material_psets.json
index 7f04748..6ffe773 100644
--- a/src/materialsdb/ifc/material_psets.json
+++ b/src/materialsdb/ifc/material_psets.json
@@ -239,16 +239,16 @@
     },
     "materialsdb.org_layer": {
         "id": {
-            "path": "id",
-            "primary_measure_type": null
+            "path": ["id"],
+            "primary_measure_type": "IfcIdentifier"
         },
         "aliases": {
-            "path": "aliases",
-            "primary_measure_type": null
+            "path": ["aliases"],
+            "primary_measure_type": "IfcLabel"
         },
         "displayorder": {
-            "path": "displayorder",
-            "primary_measure_type": null
+            "path": ["displayorder"],
+            "primary_measure_type": "IfcInteger"
         }
     },
     "materialsdb.org_thermal": {
@@ -258,7 +258,7 @@
                 "lambda_value_dry"
             ],
             "unit_factor": null,
-            "primary_measure_type": null
+            "primary_measure_type": "IfcThermalConductivityMeasure"
         },
         "W80_coef": {
             "path": [
diff --git a/src/materialsdb/ifc/project_library.py b/src/materialsdb/ifc/project_library.py
index 902155f..4ff930f 100644
--- a/src/materialsdb/ifc/project_library.py
+++ b/src/materialsdb/ifc/project_library.py
@@ -190,7 +190,7 @@ def create_materials(self, source: Materials):
                             continue
                         value = get_value(layer, definition, self.country)
                         if value:
-                            unit_factor = definition["unit_factor"] or 1
+                            unit_factor = definition.get("unit_factor", None) or 1
                             properties.append(
                                 file.create_entity(
                                     "IfcPropertySingleValue",