diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 1ff6993e..24dce4fa 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         os: [ubuntu-latest]
-        python-version: [3.8, 3.9, "3.10", "3.11"]
+        python-version: ["3.8", "3.9", "3.10", "3.11"]
     runs-on: ${{ matrix.os }}
     steps:
       - name: Clone Repository
diff --git a/supabase/client.py b/supabase/client.py
index 73182832..5870bcc4 100644
--- a/supabase/client.py
+++ b/supabase/client.py
@@ -59,12 +59,12 @@ def __init__(
         self.supabase_url = supabase_url
         self.supabase_key = supabase_key
         options.headers.update(self._get_auth_headers())
-        self.rest_url: str = f"{supabase_url}/rest/v1"
-        self.realtime_url: str = f"{supabase_url}/realtime/v1".replace("http", "ws")
-        self.auth_url: str = f"{supabase_url}/auth/v1"
+        self.rest_url = f"{supabase_url}/rest/v1"
+        self.realtime_url = f"{supabase_url}/realtime/v1".replace("http", "ws")
+        self.auth_url = f"{supabase_url}/auth/v1"
         self.storage_url = f"{supabase_url}/storage/v1"
         self.functions_url = f"{supabase_url}/functions/v1"
-        self.schema: str = options.schema
+        self.schema = options.schema
 
         # Instantiate clients.
         self.auth = self._init_supabase_auth_client(
diff --git a/supabase/lib/auth_client.py b/supabase/lib/auth_client.py
index 2e091294..10800a52 100644
--- a/supabase/lib/auth_client.py
+++ b/supabase/lib/auth_client.py
@@ -1,4 +1,4 @@
-from typing import Dict, Union
+from typing import Dict, Optional
 
 from gotrue import SyncGoTrueClient, SyncMemoryStorage, SyncSupportedStorage
 
@@ -18,14 +18,17 @@ def __init__(
         self,
         *,
         url: str,
-        headers: Dict[str, str] = {},
-        storage_key: Union[str, None] = None,
+        headers: Optional[Dict[str, str]] = None,
+        storage_key: Optional[str] = None,
         auto_refresh_token: bool = True,
         persist_session: bool = True,
         storage: SyncSupportedStorage = SyncMemoryStorage(),
-        http_client: Union[SyncClient, None] = None,
+        http_client: Optional[SyncClient] = None,
     ):
         """Instantiate SupabaseAuthClient instance."""
+        if headers is None:
+            headers = {}
+
         SyncGoTrueClient.__init__(
             self,
             url=url,
diff --git a/tests/test_client_options.py b/tests/test_client_options.py
index 3a637e5e..75361722 100644
--- a/tests/test_client_options.py
+++ b/tests/test_client_options.py
@@ -3,41 +3,41 @@
 from supabase.lib.client_options import ClientOptions
 
 
-def test__client_options__replace__returns_updated_options():
-    storage = SyncMemoryStorage()
-    storage.set_item("key", "value")
-    options = ClientOptions(
-        schema="schema",
-        headers={"key": "value"},
-        auto_refresh_token=False,
-        persist_session=False,
-        storage=storage,
-        realtime={"key": "value"},
-    )
-
-    actual = options.replace(schema="new schema")
-    expected = ClientOptions(
-        schema="new schema",
-        headers={"key": "value"},
-        auto_refresh_token=False,
-        persist_session=False,
-        storage=storage,
-        realtime={"key": "value"},
-    )
-
-    assert actual == expected
-
-
-def test__client_options__replace__updates_only_new_options():
-    # Arrange
-    storage = SyncMemoryStorage()
-    storage.set_item("key", "value")
-    options = ClientOptions(storage=storage)
-    new_options = options.replace()
-
-    # Act
-    new_options.storage.set_item("key", "new_value")
-
-    # Assert
-    assert options.storage.get_item("key") == "new_value"
-    assert new_options.storage.get_item("key") == "new_value"
+class TestClientOptions:
+    def test_replace_returns_updated_options(self):
+        storage = SyncMemoryStorage()
+        storage.set_item("key", "value")
+        options = ClientOptions(
+            schema="schema",
+            headers={"key": "value"},
+            auto_refresh_token=False,
+            persist_session=False,
+            storage=storage,
+            realtime={"key": "value"},
+        )
+
+        actual = options.replace(schema="new schema")
+        expected = ClientOptions(
+            schema="new schema",
+            headers={"key": "value"},
+            auto_refresh_token=False,
+            persist_session=False,
+            storage=storage,
+            realtime={"key": "value"},
+        )
+
+        assert actual == expected
+
+    def test_replace_updates_only_new_options(self):
+        # Arrange
+        storage = SyncMemoryStorage()
+        storage.set_item("key", "value")
+        options = ClientOptions(storage=storage)
+        new_options = options.replace()
+
+        # Act
+        new_options.storage.set_item("key", "new_value")
+
+        # Assert
+        assert options.storage.get_item("key") == "new_value"
+        assert new_options.storage.get_item("key") == "new_value"