diff --git a/.pre-commit-config.yaml b/.pre-commit-config.yaml
index d5e30d8..e292c07 100644
--- a/.pre-commit-config.yaml
+++ b/.pre-commit-config.yaml
@@ -30,6 +30,6 @@ repos:
       - id: isort
         args: ["--profile", "black", "--filter-files"]
   - repo: https://github.com/psf/black
-    rev: 19.3b0
+    rev: 22.3.0
     hooks:
       - id: black
diff --git a/joint_teapot/workers/git.py b/joint_teapot/workers/git.py
index 25f290d..715740c 100644
--- a/joint_teapot/workers/git.py
+++ b/joint_teapot/workers/git.py
@@ -7,7 +7,7 @@ from joint_teapot.utils.logger import logger
 
 current_path = sys.path[0]
 sys.path.remove(current_path)
-from git import Repo
+from git import Repo  # type: ignore
 from git.exc import GitCommandError
 
 sys.path.insert(0, current_path)
diff --git a/joint_teapot/workers/joj.py b/joint_teapot/workers/joj.py
index eea71e8..6d74e6e 100644
--- a/joint_teapot/workers/joj.py
+++ b/joint_teapot/workers/joj.py
@@ -16,6 +16,8 @@ class JOJ:
         self.submitter = JOJSubmitter(sid, logger)
 
     def submit_dir(self, problem_url: str, path: str, lang: str) -> Tuple[int, str]:
+        if lang not in list(Language):
+            raise Exception(f"unsupported language '{lang}' for JOJ")
         exclude_paths = [".git"]
         zip_buffer = io.BytesIO()
         zip_buffer.name = f"{os.path.basename(path)}.zip"