diff --git a/.coveragerc b/.coveragerc
index 9ba3d3fe6..4192b8cf8 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -6,6 +6,8 @@ omit =
     */samples/*
     */conftest.py
     */google-cloud-sdk/lib/*
+    # NOTE: Temporarily disabling coverage for `_requests_base.py`.
+    */_requests_base.py
 exclude_lines =
     # Re-enable the standard pragma
     pragma: NO COVER
diff --git a/google/auth/transport/_requests_base.py b/google/auth/transport/_requests_base.py
index ec718d909..0608223d8 100644
--- a/google/auth/transport/_requests_base.py
+++ b/google/auth/transport/_requests_base.py
@@ -13,7 +13,8 @@
 # limitations under the License.
 
 """Transport adapter for Base Requests."""
-
+# NOTE: The coverage for this file is temporarily disabled in `.coveragerc`
+# since it is currently unused.
 
 import abc
 
diff --git a/google/auth/transport/requests.py b/google/auth/transport/requests.py
index 68f67c59b..23a69783d 100644
--- a/google/auth/transport/requests.py
+++ b/google/auth/transport/requests.py
@@ -38,7 +38,6 @@
 from google.auth import exceptions
 from google.auth import transport
 import google.auth.transport._mtls_helper
-from google.auth.transport._requests_base import _BaseAuthorizedSession
 from google.oauth2 import service_account
 
 _LOGGER = logging.getLogger(__name__)
@@ -293,7 +292,7 @@ def proxy_manager_for(self, *args, **kwargs):
         return super(_MutualTlsOffloadAdapter, self).proxy_manager_for(*args, **kwargs)
 
 
-class AuthorizedSession(requests.Session, _BaseAuthorizedSession):
+class AuthorizedSession(requests.Session):
     """A Requests Session class with credentials.
 
     This class is used to perform requests to API endpoints that require
@@ -390,7 +389,7 @@ def __init__(
         default_host=None,
     ):
         super(AuthorizedSession, self).__init__()
-        _BaseAuthorizedSession.__init__(self, credentials)
+        self.credentials = credentials
         self._refresh_status_codes = refresh_status_codes
         self._max_refresh_attempts = max_refresh_attempts
         self._refresh_timeout = refresh_timeout
diff --git a/system_tests/secrets.tar.enc b/system_tests/secrets.tar.enc
index 2d3f631e9..d0d4ce702 100644
Binary files a/system_tests/secrets.tar.enc and b/system_tests/secrets.tar.enc differ