diff --git a/src/blenderbim/blenderbim/bim/module/material/ui.py b/src/blenderbim/blenderbim/bim/module/material/ui.py
index e9f369b65c..17ff769851 100644
--- a/src/blenderbim/blenderbim/bim/module/material/ui.py
+++ b/src/blenderbim/blenderbim/bim/module/material/ui.py
@@ -343,7 +343,7 @@ class BIM_UL_materials(UIList):
                     row.operator(
                         "bim.expand_material_category", text="", emboss=False, icon="DISCLOSURE_TRI_RIGHT"
                     ).category = item.name
-                row.label(text=item.name or "Uncategorised")
+                row.label(text=item.name)
             else:
                 row.label(text="", icon="BLANK1")
                 row.label(text=item.name, icon="MATERIAL")
diff --git a/src/blenderbim/blenderbim/tool/material.py b/src/blenderbim/blenderbim/tool/material.py
index 4a72301f2f..6dbb345311 100644
--- a/src/blenderbim/blenderbim/tool/material.py
+++ b/src/blenderbim/blenderbim/tool/material.py
@@ -24,6 +24,7 @@ import blenderbim.tool as tool
 import blenderbim.bim.helper
 import ifcopenshell.util.unit
 import ifcopenshell.util.element
+from collections import defaultdict
 from typing import Union, Any
 
 
@@ -67,12 +68,16 @@ class Material(blenderbim.core.tool.Material):
         elif material_type == "IfcMaterialList":
             get_name = lambda x: "Unnamed"
         materials = sorted(tool.Ifc.get().by_type(material_type), key=get_name)
-        categories = {}
+        categories = defaultdict(list)
         if material_type == "IfcMaterial":
-            [categories.setdefault(getattr(m, "Category", "Uncategorised"), []).append(m) for m in materials]
+            for m in materials:
+                # IfcMaterial has Category since IFC4.
+                category = getattr(m, "Category", None)
+                category = category or "Uncategorised"
+                categories[category].append(m)
             for category, mats in categories.items():
                 cat = props.materials.add()
-                cat.name = category or ""
+                cat.name = category
                 cat.is_category = True
                 cat.is_expanded = cat.name in expanded_categories
                 for material in mats if cat.is_expanded else []: