diff --git a/patroni/api.py b/patroni/api.py
index f461811b..7be2a049 100644
--- a/patroni/api.py
+++ b/patroni/api.py
@@ -1541,11 +1541,11 @@ class RestApiServer(ThreadingMixIn, HTTPServer, Thread):
         if self.__ssl_options.get('certfile'):
             import ssl
             try:
-                ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
-                crts = ctx.load_verify_locations(self.__ssl_options['certfile'])
-                if crts:
-                    return crts[0].get('serialNumber')
-            except Exception as e:
+                crt: Dict[str, Any] = ssl._ssl._test_decode_cert(self.__ssl_options['certfile'])  # pyright: ignore
+                if TYPE_CHECKING:  # pragma: no cover
+                    assert isinstance(crt, dict)
+                return crt.get('serialNumber')
+            except ssl.SSLError as e:
                 logger.error('Failed to get serial number from certificate %s: %r', self.__ssl_options['certfile'], e)
 
     def reload_local_certificate(self) -> Optional[bool]:
diff --git a/tests/test_api.py b/tests/test_api.py
index 166d3eb1..25342dca 100644
--- a/tests/test_api.py
+++ b/tests/test_api.py
@@ -180,7 +180,6 @@ class MockRestApiServer(RestApiServer):
 
 @patch('ssl.SSLContext.load_cert_chain', Mock())
 @patch('ssl.SSLContext.wrap_socket', Mock(return_value=0))
-@patch('ssl.SSLContext.load_verify_locations', Mock(return_value=[Mock()]))
 @patch.object(HTTPServer, '__init__', Mock())
 class TestRestApiHandler(unittest.TestCase):
 
@@ -589,7 +588,6 @@ class TestRestApiServer(unittest.TestCase):
     @patch('ssl.SSLContext.load_cert_chain', Mock())
     @patch('ssl.SSLContext.set_ciphers', Mock())
     @patch('ssl.SSLContext.wrap_socket', Mock(return_value=0))
-    @patch('ssl.SSLContext.load_verify_locations', Mock(return_value=[Mock()]))
     @patch.object(HTTPServer, '__init__', Mock())
     def setUp(self):
         self.srv = MockRestApiServer(Mock(), '', {'listen': '*:8008', 'certfile': 'a', 'verify_client': 'required',
@@ -652,10 +650,9 @@ class TestRestApiServer(unittest.TestCase):
         mock_get_request.return_value = (self.__create_socket(), ('127.0.0.1', 55555))
         self.srv._handle_request_noblock()
 
-    @patch('ssl.SSLContext.load_verify_locations', Mock(return_value=[Mock()]))
+    @patch('ssl._ssl._test_decode_cert', Mock())
     def test_reload_local_certificate(self):
         self.assertTrue(self.srv.reload_local_certificate())
 
-    @patch('ssl.SSLContext.load_verify_locations', Mock(side_effect=Exception))
     def test_get_certificate_serial_number(self):
         self.assertIsNone(self.srv.get_certificate_serial_number())