diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1e116b6..23eda6c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -40,6 +40,9 @@ jobs:
         uv run ruff check .
         uv run ruff format --check .
 
+    - name: Type check with mypy
+      run: uv run mypy oscilloscope-rp2040
+
     - name: Run Tests
       run: uv run pytest
 
diff --git a/oscilloscope-rp2040/sysaudio/io.py b/oscilloscope-rp2040/sysaudio/io.py
index 245781a..623b8c2 100644
--- a/oscilloscope-rp2040/sysaudio/io.py
+++ b/oscilloscope-rp2040/sysaudio/io.py
@@ -2,7 +2,8 @@
 import os
 import sys
 from datetime import datetime
-from typing import Any, Optional, Tuple
+from pathlib import Path
+from typing import Any, Optional, Tuple, Union
 
 import numpy as np
 import pandas as pd
@@ -63,7 +64,7 @@ def save_signal(
     return path
 
 
-def load_signal(filepath: str) -> Tuple[np.ndarray, float]:
+def load_signal(filepath: Union[str, Path]) -> Tuple[np.ndarray, float]:
     """
     Robust loader for .npz files.