diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index dbc16d0..e6992ae 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -30,4 +30,6 @@ jobs:
         run: python3 -m pytest
 
       - name: Run mypy
-        run: mypy .
+        run: |
+          python3 -m mypy --strict src
+          python3 -m mypy test
diff --git a/src/llm_utils/llm_utils.py b/src/llm_utils/llm_utils.py
index 95de03f..cc79ec9 100644
--- a/src/llm_utils/llm_utils.py
+++ b/src/llm_utils/llm_utils.py
@@ -140,7 +140,7 @@ def read_lines(file_path: str, start_line: int, end_line: int) -> tuple[list[str
     # Prevent pathological case where lines are REALLY long.
     max_chars_per_line = 128
 
-    def truncate(s, l):
+    def truncate(s: str, l: int) -> str:
         """
         Truncate the string to at most the given length, adding ellipses if truncated.
         """