diff --git a/src/socketio/async_server.py b/src/socketio/async_server.py
index 7e9c872..65dcb38 100644
--- a/src/socketio/async_server.py
+++ b/src/socketio/async_server.py
@@ -301,6 +301,8 @@ class AsyncServer(base_server.BaseServer):
 
         Note: this method is a coroutine.
         """
+        if room is None:
+            raise ValueError('The room name cannot be None')
         namespace = namespace or '/'
         self.logger.info('%s is entering room %s [%s]', sid, room, namespace)
         await self.manager.enter_room(sid, namespace, room)
@@ -317,6 +319,8 @@ class AsyncServer(base_server.BaseServer):
 
         Note: this method is a coroutine.
         """
+        if room is None:
+            raise ValueError('The room name cannot be None')
         namespace = namespace or '/'
         self.logger.info('%s is leaving room %s [%s]', sid, room, namespace)
         await self.manager.leave_room(sid, namespace, room)
@@ -332,6 +336,8 @@ class AsyncServer(base_server.BaseServer):
 
         Note: this method is a coroutine.
         """
+        if room is None:
+            raise ValueError('The room name cannot be None')
         namespace = namespace or '/'
         self.logger.info('room %s is closing [%s]', room, namespace)
         await self.manager.close_room(room, namespace)
diff --git a/src/socketio/server.py b/src/socketio/server.py
index 143d27e..deebd08 100644
--- a/src/socketio/server.py
+++ b/src/socketio/server.py
@@ -281,6 +281,8 @@ class Server(base_server.BaseServer):
         :param namespace: The Socket.IO namespace for the event. If this
                           argument is omitted the default namespace is used.
         """
+        if room is None:
+            raise ValueError('The room name cannot be None')
         namespace = namespace or '/'
         self.logger.info('%s is entering room %s [%s]', sid, room, namespace)
         self.manager.enter_room(sid, namespace, room)
@@ -295,6 +297,8 @@ class Server(base_server.BaseServer):
         :param namespace: The Socket.IO namespace for the event. If this
                           argument is omitted the default namespace is used.
         """
+        if room is None:
+            raise ValueError('The room name cannot be None')
         namespace = namespace or '/'
         self.logger.info('%s is leaving room %s [%s]', sid, room, namespace)
         self.manager.leave_room(sid, namespace, room)
@@ -308,6 +312,8 @@ class Server(base_server.BaseServer):
         :param namespace: The Socket.IO namespace for the event. If this
                           argument is omitted the default namespace is used.
         """
+        if room is None:
+            raise ValueError('The room name cannot be None')
         namespace = namespace or '/'
         self.logger.info('room %s is closing [%s]', room, namespace)
         self.manager.close_room(room, namespace)
diff --git a/tests/async/test_server.py b/tests/async/test_server.py
index c3c0903..23f9904 100644
--- a/tests/async/test_server.py
+++ b/tests/async/test_server.py
@@ -252,6 +252,22 @@ class TestAsyncServer:
         await s.close_room('room')
         s.manager.close_room.assert_awaited_once_with('room', '/')
 
+    async def test_enter_leave_close_room_none_rejected(self, eio):
+        # None is the reserved default room that stores the sid<->eio_sid
+        # mapping; the public room API must reject it instead of corrupting
+        # the manager's internal data structures (issue #1447).
+        mgr = self._get_mock_manager()
+        s = async_server.AsyncServer(client_manager=mgr)
+        with pytest.raises(ValueError):
+            await s.enter_room('123', None, namespace='/foo')
+        with pytest.raises(ValueError):
+            await s.leave_room('123', None, namespace='/foo')
+        with pytest.raises(ValueError):
+            await s.close_room(None, namespace='/foo')
+        s.manager.enter_room.assert_not_awaited()
+        s.manager.leave_room.assert_not_awaited()
+        s.manager.close_room.assert_not_awaited()
+
     async def test_rooms(self, eio):
         mgr = self._get_mock_manager()
         s = async_server.AsyncServer(client_manager=mgr)
diff --git a/tests/common/test_server.py b/tests/common/test_server.py
index d8d80dc..2ebfd3f 100644
--- a/tests/common/test_server.py
+++ b/tests/common/test_server.py
@@ -254,6 +254,22 @@ class TestServer:
         s.close_room('room')
         s.manager.close_room.assert_called_once_with('room', '/')
 
+    def test_enter_leave_close_room_none_rejected(self, eio):
+        # None is the reserved default room that stores the sid<->eio_sid
+        # mapping; the public room API must reject it instead of corrupting
+        # the manager's internal data structures (issue #1447).
+        mgr = mock.MagicMock()
+        s = server.Server(client_manager=mgr)
+        with pytest.raises(ValueError):
+            s.enter_room('123', None, namespace='/foo')
+        with pytest.raises(ValueError):
+            s.leave_room('123', None, namespace='/foo')
+        with pytest.raises(ValueError):
+            s.close_room(None, namespace='/foo')
+        s.manager.enter_room.assert_not_called()
+        s.manager.leave_room.assert_not_called()
+        s.manager.close_room.assert_not_called()
+
     def test_rooms(self, eio):
         mgr = mock.MagicMock()
         s = server.Server(client_manager=mgr)