diff --git a/pyproject.toml b/pyproject.toml
index 0b907b2..8a7126c 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -131,3 +131,6 @@ commands = [
   ["coverage", "report"],
 ]
 dependency_groups = ["dev"]
+
+[tool.ty.rules]
+all = "error"
diff --git a/sqlite_export_for_ynab/_main.py b/sqlite_export_for_ynab/_main.py
index cca4c02..136d3dc 100644
--- a/sqlite_export_for_ynab/_main.py
+++ b/sqlite_export_for_ynab/_main.py
@@ -14,6 +14,7 @@
 from typing import Any
 from typing import Literal
 from typing import overload
+from typing import override
 from typing import TYPE_CHECKING
 
 import aiosqlite
@@ -67,6 +68,7 @@ def __init__(self, separator: str = "/", table_column: Column | None = None):
             self.separator = separator
             super().__init__(table_column=table_column)
 
+        @override
         def render(self, task: Task) -> Text:
             """Show completed/total."""
             completed = int(task.completed)