diff --git a/pyproject.toml b/pyproject.toml
index dbed082..ccdf02f 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -166,6 +166,8 @@ strict = true
 exclude = [
   "^tests/data",
 ]
+warn_unreachable = true
+enable_error_code = ["ignore-without-code", "redundant-expr", "truthy-bool"]
 
 [[tool.mypy.overrides]]
 module = 'bids_validator._version'
diff --git a/src/bids_validator/types/files.py b/src/bids_validator/types/files.py
index 4cbe652..7d044e5 100644
--- a/src/bids_validator/types/files.py
+++ b/src/bids_validator/types/files.py
@@ -26,7 +26,7 @@ class FileTree:
 
     def __attrs_post_init__(self) -> None:
         if self.is_dir is None:
-            object.__setattr__(self, 'is_dir', self.path_obj.is_dir())
+            object.__setattr__(self, 'is_dir', self.path_obj.is_dir())  # type: ignore[unreachable]
         object.__setattr__(
             self,
             'children',