diff --git a/src/ifcopenshell-python/ifcopenshell/util/doc.py b/src/ifcopenshell-python/ifcopenshell/util/doc.py
index d041d6b628..5a8115eb30 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/doc.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/doc.py
@@ -20,8 +20,10 @@ import json
 from pathlib import Path
 import copy
 import ifcopenshell
+import ifcopenshell.ifcopenshell_wrapper as ifcopenshell_wrapper
 import ifcopenshell.util.attribute
 import ifcopenshell.util.schema
+from typing import Optional, Literal
 
 try:
     import glob
@@ -58,8 +60,8 @@ IFC4x3_SPEC_URL_TEMPLATE = "https://ifc43-docs.standards.buildingsmart.org/IFC/R
 # child -> description
 # note: in IFC4x3 there is no children[] for properties
 
-
-SCHEMA_FILES = {
+SUPPORTED_SCHEMA = Literal["IFC2X3", "IFC4", "IFC4X3"]
+SCHEMA_FILES: dict[SUPPORTED_SCHEMA, dict] = {
     "IFC2X3": {
         "entities": BASE_MODULE_PATH / "schema/ifc2x3_entities.json",
         "properties": BASE_MODULE_PATH / "schema/ifc2x3_properties.json",
@@ -81,7 +83,11 @@ SCHEMA_FILES = {
 }
 
 db = None
-schema_by_name = {"IFC2X3": None, "IFC4": None, "IFC4X3": None}
+schema_by_name: dict[SUPPORTED_SCHEMA, Optional[ifcopenshell_wrapper.schema_definition]] = {
+    "IFC2X3": None,
+    "IFC4": None,
+    "IFC4X3": None,
+}
 
 
 def get_db(version):
@@ -103,11 +109,12 @@ def get_db(version):
     return db.get(version)
 
 
-def get_schema_by_name(version: str):
+def get_schema_by_name(version: str) -> ifcopenshell_wrapper.schema_definition:
     global schema_by_name
     version = ifcopenshell.util.schema.get_fallback_schema(version)
     if not schema_by_name[version]:
-        schema_by_name[version] = ifcopenshell.ifcopenshell_wrapper.schema_by_name(version)
+        schema_name = "IFC4X3_ADD2" if version == "IFC4X3" else version
+        schema_by_name[version] = ifcopenshell_wrapper.schema_by_name(schema_name)
     return schema_by_name[version]