diff --git a/at_client/connections/atconnection.py b/at_client/connections/atconnection.py
index 1c41125..173fcdd 100644
--- a/at_client/connections/atconnection.py
+++ b/at_client/connections/atconnection.py
@@ -98,8 +98,16 @@ def disconnect(self):
         """
         Close the socket connection.
         """
-        self._secure_root_socket.close()
-        self._connected = False
+        # Always clear _connected, even if close() fails on an already-broken socket
+        # (e.g. "Bad file descriptor"). Otherwise _connected stays True and the monitor
+        # restart path (guarded by `if not self._connected`) never rebuilds the socket,
+        # so the client silently stops receiving notifications until it is recreated.
+        try:
+            self._secure_root_socket.close()
+        except Exception:
+            pass
+        finally:
+            self._connected = False
 
     @abstractmethod
     def parse_raw_response(self, raw_response:str) -> Response:
diff --git a/test/disconnect_test.py b/test/disconnect_test.py
new file mode 100644
index 0000000..4cebb6e
--- /dev/null
+++ b/test/disconnect_test.py
@@ -0,0 +1,35 @@
+import unittest
+from unittest.mock import MagicMock
+
+from at_client.connections.atconnection import AtConnection
+
+
+class _ConcreteConnection(AtConnection):
+    """Minimal concrete subclass so we can exercise the base disconnect()."""
+
+    def parse_raw_response(self, raw_response):
+        return None
+
+
+class DisconnectTest(unittest.TestCase):
+    """disconnect() must always clear _connected, even if the socket close fails."""
+
+    def test_disconnect_clears_connected_on_clean_close(self):
+        conn = _ConcreteConnection.__new__(_ConcreteConnection)  # bypass network __init__
+        conn._connected = True
+        conn._secure_root_socket = MagicMock()
+        conn.disconnect()
+        conn._secure_root_socket.close.assert_called_once()
+        self.assertFalse(conn._connected)
+
+    def test_disconnect_clears_connected_even_when_close_raises(self):
+        conn = _ConcreteConnection.__new__(_ConcreteConnection)
+        conn._connected = True
+        conn._secure_root_socket = MagicMock()
+        conn._secure_root_socket.close.side_effect = OSError(9, "Bad file descriptor")
+        conn.disconnect()  # must not propagate
+        self.assertFalse(conn._connected)  # so the restart path can rebuild the socket
+
+
+if __name__ == "__main__":
+    unittest.main()