diff --git a/google/auth/external_account_authorized_user.py b/google/auth/external_account_authorized_user.py
index 2594e048f..b631c1894 100644
--- a/google/auth/external_account_authorized_user.py
+++ b/google/auth/external_account_authorized_user.py
@@ -343,7 +343,7 @@ def revoke(self, request):
             request, self._refresh_token_val, "refresh_token", self._revoke_url
         )
         self.token = None
-        self._refresh_token = None
+        self._refresh_token_val = None
 
     @_helpers.copy_docstring(credentials.Credentials)
     def get_cred_info(self):
diff --git a/google/oauth2/_credentials_async.py b/google/oauth2/_credentials_async.py
index b5561aae0..54b5e16fc 100644
--- a/google/oauth2/_credentials_async.py
+++ b/google/oauth2/_credentials_async.py
@@ -50,7 +50,7 @@ class Credentials(oauth2_credentials.Credentials):
     @_helpers.copy_docstring(credentials.Credentials)
     async def refresh(self, request):
         if (
-            self._refresh_token is None
+            self._refresh_token_val is None
             or self._token_uri is None
             or self._client_id is None
             or self._client_secret is None
@@ -70,7 +70,7 @@ async def refresh(self, request):
         ) = await reauth.refresh_grant(
             request,
             self._token_uri,
-            self._refresh_token,
+            self._refresh_token_val,
             self._client_id,
             self._client_secret,
             scopes=self._scopes,
@@ -80,7 +80,7 @@ async def refresh(self, request):
 
         self.token = access_token
         self.expiry = expiry
-        self._refresh_token = refresh_token
+        self._refresh_token_val = refresh_token
         self._id_token = grant_response.get("id_token")
         self._rapt_token = rapt_token
 
diff --git a/google/oauth2/credentials.py b/google/oauth2/credentials.py
index 6e158089f..c29b6f87c 100644
--- a/google/oauth2/credentials.py
+++ b/google/oauth2/credentials.py
@@ -139,7 +139,7 @@ def __init__(
         super(Credentials, self).__init__()
         self.token = token
         self.expiry = expiry
-        self._refresh_token = refresh_token
+        self._refresh_token_val = refresh_token
         self._id_token = id_token
         self._scopes = scopes
         self._default_scopes = default_scopes
@@ -178,7 +178,7 @@ def __setstate__(self, d):
         all the attributes."""
         self.token = d.get("token")
         self.expiry = d.get("expiry")
-        self._refresh_token = d.get("_refresh_token")
+        self._refresh_token_val = d.get("_refresh_token_val")
         self._id_token = d.get("_id_token")
         self._scopes = d.get("_scopes")
         self._default_scopes = d.get("_default_scopes")
@@ -203,7 +203,7 @@ def __setstate__(self, d):
     @property
     def refresh_token(self):
         """Optional[str]: The OAuth 2.0 refresh token."""
-        return self._refresh_token
+        return self._refresh_token_val
 
     @property
     def scopes(self):
@@ -350,6 +350,9 @@ def with_universe_domain(self, universe_domain):
     def _metric_header_for_usage(self):
         return metrics.CRED_TYPE_USER
 
+    def _refresh_token(self, request):
+        return self.refresh(request)
+
     @_helpers.copy_docstring(credentials.Credentials)
     def refresh(self, request):
         if self._universe_domain != credentials.DEFAULT_UNIVERSE_DOMAIN:
@@ -368,7 +371,7 @@ def refresh(self, request):
         # available. This is useful in general when tokens are obtained by calling
         # some external process on demand. It is particularly useful for retrieving
         # downscoped tokens from a token broker.
-        if self._refresh_token is None and self.refresh_handler:
+        if self._refresh_token_val is None and self.refresh_handler:
             token, expiry = self.refresh_handler(request, scopes=scopes)
             # Validate returned data.
             if not isinstance(token, str):
@@ -389,7 +392,7 @@ def refresh(self, request):
             return
 
         if (
-            self._refresh_token is None
+            self._refresh_token_val is None
             or self._token_uri is None
             or self._client_id is None
             or self._client_secret is None
@@ -409,7 +412,7 @@ def refresh(self, request):
         ) = reauth.refresh_grant(
             request,
             self._token_uri,
-            self._refresh_token,
+            self._refresh_token_val,
             self._client_id,
             self._client_secret,
             scopes=scopes,
@@ -419,7 +422,7 @@ def refresh(self, request):
 
         self.token = access_token
         self.expiry = expiry
-        self._refresh_token = refresh_token
+        self._refresh_token_val = refresh_token
         self._id_token = grant_response.get("id_token")
         self._rapt_token = rapt_token
 
diff --git a/tests/test__oauth2client.py b/tests/test__oauth2client.py
index 2d4a809bb..ac6164bdc 100644
--- a/tests/test__oauth2client.py
+++ b/tests/test__oauth2client.py
@@ -52,7 +52,7 @@ def test__convert_oauth2_credentials():
     new_credentials = _oauth2client._convert_oauth2_credentials(old_credentials)
 
     assert new_credentials.token == old_credentials.access_token
-    assert new_credentials._refresh_token == old_credentials.refresh_token
+    assert new_credentials._refresh_token_val == old_credentials.refresh_token
     assert new_credentials._client_id == old_credentials.client_id
     assert new_credentials._client_secret == old_credentials.client_secret
     assert new_credentials._token_uri == old_credentials.token_uri
diff --git a/tests/test_external_account_authorized_user.py b/tests/test_external_account_authorized_user.py
index 0a54af56d..53114d8ac 100644
--- a/tests/test_external_account_authorized_user.py
+++ b/tests/test_external_account_authorized_user.py
@@ -367,7 +367,7 @@ def test_revoke_auth_success(self):
             ),
         )
         assert creds.token is None
-        assert creds._refresh_token is None
+        assert creds._refresh_token_val is None
 
     def test_revoke_without_revoke_url(self):
         request = self.make_mock_request()