diff --git a/io_scene_psk_psa/helpers.py b/io_scene_psk_psa/helpers.py
index f522f72..0e5c282 100644
--- a/io_scene_psk_psa/helpers.py
+++ b/io_scene_psk_psa/helpers.py
@@ -47,7 +47,7 @@ def get_nla_strips_in_timeframe(animation_data, frame_min, frame_max) -> List[Nl
     return strips
 
 
-def populate_bone_group_list(armature_object: Object, bone_group_list: bpy.types.Collection) -> None:
+def populate_bone_group_list(armature_object: Object, bone_group_list: bpy.props.CollectionProperty) -> None:
     """
     Updates the bone group collection.
 
@@ -94,7 +94,7 @@ def get_psa_sequence_name(action, should_use_original_sequence_name):
 
 
 def check_bone_names(bone_names: Iterable[str]):
-    pattern = re.compile(r'^[a-zA-Z0-9_\- ]+$')
+    pattern = re.compile(r'^[a-zA-Z\d_\- ]+$')
     invalid_bone_names = [x for x in bone_names if pattern.match(x) is None]
     if len(invalid_bone_names) > 0:
         raise RuntimeError(f'The following bone names are invalid: {invalid_bone_names}.\n'
diff --git a/io_scene_psk_psa/psk/reader.py b/io_scene_psk_psa/psk/reader.py
index 414a5f4..7935ec6 100644
--- a/io_scene_psk_psa/psk/reader.py
+++ b/io_scene_psk_psa/psk/reader.py
@@ -12,7 +12,7 @@ def _read_types(fp, data_class, section: Section, data):
         offset += section.data_size
 
 
-def read_psk(path) -> Psk:
+def read_psk(path: str) -> Psk:
     psk = Psk()
     with open(path, 'rb') as fp:
         while fp.read(1):