diff --git a/src/bonsai/bonsai/bim/module/tester/operator.py b/src/bonsai/bonsai/bim/module/tester/operator.py
index b2c8e51d20..3b963d753d 100644
--- a/src/bonsai/bonsai/bim/module/tester/operator.py
+++ b/src/bonsai/bonsai/bim/module/tester/operator.py
@@ -29,6 +29,7 @@ import ifcopenshell
 import bonsai.tool as tool
 import bonsai.bim.handler
 from pathlib import Path
+from typing import Union
 
 
 class ExecuteIfcTester(bpy.types.Operator):
@@ -66,7 +67,7 @@ class ExecuteIfcTester(bpy.types.Operator):
         bonsai.bim.handler.refresh_ui_data()
         return {"FINISHED"}
 
-    def execute_tester(self, ifc_data, ifc_path, specs_path):
+    def execute_tester(self, ifc_data: ifcopenshell.file, ifc_path: str, specs_path: str) -> Union[set[str], None]:
         props = bpy.context.scene.IfcTesterProperties
 
         with tempfile.TemporaryDirectory() as dirpath:
diff --git a/src/ifccsv/ifccsv.py b/src/ifccsv/ifccsv.py
index c41bf2d040..e474724ee0 100755
--- a/src/ifccsv/ifccsv.py
+++ b/src/ifccsv/ifccsv.py
@@ -29,7 +29,7 @@ import ifcopenshell.util.selector
 import ifcopenshell.util.element
 import ifcopenshell.util.schema
 from statistics import mean
-from typing import Optional, Union, Literal
+from typing import Optional, Union, Literal, Iterable
 
 try:
     from odf.namespaces import OFFICENS
@@ -65,6 +65,9 @@ FILE_FORMAT = Literal[
 
 
 class IfcCsv:
+    attributes: list[str]
+    headers: list[str]
+
     def __init__(self):
         self.headers = []
         self.results = []
@@ -73,9 +76,9 @@ class IfcCsv:
     def export(
         self,
         ifc_file: ifcopenshell.file,
-        elements: ifcopenshell.entity_instance,
-        attributes,
-        headers=None,
+        elements: Iterable[ifcopenshell.entity_instance],
+        attributes: Union[list[str], None],
+        headers: Optional[list[str]] = None,
         output=None,
         format: FILE_FORMAT = None,
         should_preserve_existing: bool = False,
diff --git a/src/ifcopenshell-python/ifcopenshell/guid.py b/src/ifcopenshell-python/ifcopenshell/guid.py
index d31f744166..5be73b6bd5 100644
--- a/src/ifcopenshell-python/ifcopenshell/guid.py
+++ b/src/ifcopenshell-python/ifcopenshell/guid.py
@@ -33,7 +33,7 @@ from functools import reduce
 chars = string.digits + string.ascii_uppercase + string.ascii_lowercase + "_$"
 
 
-def compress(g):
+def compress(g: str) -> str:
     bs = [int(g[i : i + 2], 16) for i in range(0, len(g), 2)]
 
     def b64(v, l=4):
@@ -42,7 +42,7 @@ def compress(g):
     return "".join([b64(bs[0], 2)] + [b64((bs[i] << 16) + (bs[i + 1] << 8) + bs[i + 2]) for i in range(1, 16, 3)])
 
 
-def expand(g):
+def expand(g: str) -> str:
     def b64(v):
         return reduce(lambda a, b: a * 64 + b, map(lambda c: chars.index(c), v))
 
@@ -53,9 +53,9 @@ def expand(g):
     return "".join(["%02x" % b for b in bs])
 
 
-def split(g):
+def split(g: str) -> str:
     return "{%s-%s-%s-%s-%s}" % (g[:8], g[8:12], g[12:16], g[16:20], g[20:])
 
 
-def new():
+def new() -> str:
     return compress(uuid.uuid4().hex)
diff --git a/src/ifcopenshell-python/ifcopenshell/util/selector.py b/src/ifcopenshell-python/ifcopenshell/util/selector.py
index 8497e99a07..5995fe6d32 100644
--- a/src/ifcopenshell-python/ifcopenshell/util/selector.py
+++ b/src/ifcopenshell-python/ifcopenshell/util/selector.py
@@ -23,15 +23,15 @@ import ifcopenshell.api.pset
 import ifcopenshell.api.geometry
 import ifcopenshell.util
 import ifcopenshell.util.attribute
-import ifcopenshell.util.fm
-import ifcopenshell.util.unit
-import ifcopenshell.util.element
-import ifcopenshell.util.placement
-import ifcopenshell.util.geolocation
 import ifcopenshell.util.classification
+import ifcopenshell.util.element
+import ifcopenshell.util.fm
+import ifcopenshell.util.geolocation
+import ifcopenshell.util.placement
 import ifcopenshell.util.schema
 import ifcopenshell.util.shape
 import ifcopenshell.util.system
+import ifcopenshell.util.unit
 from decimal import Decimal
 from typing import Optional, Any, Union, Iterable
 
diff --git a/src/ifcopenshell-python/ifcopenshell/validate.py b/src/ifcopenshell-python/ifcopenshell/validate.py
index 7b8d68e917..1caf969f42 100644
--- a/src/ifcopenshell-python/ifcopenshell/validate.py
+++ b/src/ifcopenshell-python/ifcopenshell/validate.py
@@ -393,6 +393,7 @@ def validate(f: Union[ifcopenshell.file, str], logger: Logger, express_rules=Fal
                 logger.error(f"Unsupported schema: {schema_name}")
                 return
 
+        assert isinstance(f, ifcopenshell.file)
         log_internal_cpp_errors(f, filename, logger)
 
     validate_ifc_header(f, logger)