diff --git a/livekit-api/livekit/api/access_token.py b/livekit-api/livekit/api/access_token.py
index cba3d9df..f8b6fa22 100644
--- a/livekit-api/livekit/api/access_token.py
+++ b/livekit-api/livekit/api/access_token.py
@@ -65,9 +65,9 @@ class VideoGrants:
 @dataclasses.dataclass
 class Claims:
     exp: int = 0
-    iss: str = "" # api key
+    iss: str = ""  # api key
     nbf: int = 0
-    sub: str = "" # identity
+    sub: str = ""  # identity
 
     name: str = ""
     video: VideoGrants = dataclasses.field(default_factory=VideoGrants)
@@ -165,7 +165,8 @@ def verify(self, token: str) -> Claims:
 
 
 def camel_to_snake(str):
-   return re.sub(r'(?<!^)(?=[A-Z])', '_', str).lower()
+    return re.sub(r"(?<!^)(?=[A-Z])", "_", str).lower()
+
 
 def snake_to_camel(str):
-    return ''.join(word.title() for word in name.split('_'))
+    return "".join(word.title() for word in name.split("_"))
diff --git a/livekit-api/tests/test_access_token.py b/livekit-api/tests/test_access_token.py
index 8572b4f0..abeb0916 100644
--- a/livekit-api/tests/test_access_token.py
+++ b/livekit-api/tests/test_access_token.py
@@ -19,7 +19,7 @@ def test_verify_token():
 
     token_verifier = TokenVerifier(TEST_API_KEY, TEST_API_SECRET)
     claims = token_verifier.verify(token)
-    
+
     assert claims.sub == "test_identity"
     assert claims.metadata == "test_metadata"
     assert claims.video == grants
@@ -36,6 +36,11 @@ def test_verify_token_invalid():
     with pytest.raises(Exception):
         token_verifier.verify(token)
 
+    token_verifier = TokenVerifier("invalid_key", TEST_API_SECRET)
+    with pytest.raises(Exception):
+        token_verifier.verify(token)
+
+
 def test_verify_token_expired():
     token = (
         AccessToken(TEST_API_KEY, TEST_API_SECRET)
@@ -44,6 +49,8 @@ def test_verify_token_expired():
         .to_jwt()
     )
 
-    token_verifier = TokenVerifier(TEST_API_KEY, TEST_API_SECRET, leeway=datetime.timedelta(seconds=0))
+    token_verifier = TokenVerifier(
+        TEST_API_KEY, TEST_API_SECRET, leeway=datetime.timedelta(seconds=0)
+    )
     with pytest.raises(Exception):
         token_verifier.verify(token)