diff --git a/src/socketio/async_server.py b/src/socketio/async_server.py
index 7e9c872..bcffb35 100644
--- a/src/socketio/async_server.py
+++ b/src/socketio/async_server.py
@@ -590,6 +590,8 @@ class AsyncServer(base_server.BaseServer):
         if not self.manager.is_connected(sid, namespace):  # pragma: no cover
             return
         self.manager.pre_disconnect(sid, namespace=namespace)
+        if eio_sid in self._binary_packet:
+            del self._binary_packet[eio_sid]
         await self._trigger_event('disconnect', namespace, sid,
                                   reason or self.reason.CLIENT_DISCONNECT)
         await self.manager.disconnect(sid, namespace, ignore_queue=True)
diff --git a/src/socketio/server.py b/src/socketio/server.py
index 143d27e..6af30f3 100644
--- a/src/socketio/server.py
+++ b/src/socketio/server.py
@@ -571,6 +571,8 @@ class Server(base_server.BaseServer):
         if not self.manager.is_connected(sid, namespace):  # pragma: no cover
             return
         self.manager.pre_disconnect(sid, namespace=namespace)
+        if eio_sid in self._binary_packet:
+            del self._binary_packet[eio_sid]
         self._trigger_event('disconnect', namespace, sid,
                             reason or self.reason.CLIENT_DISCONNECT)
         self.manager.disconnect(sid, namespace, ignore_queue=True)
diff --git a/tests/async/test_server.py b/tests/async/test_server.py
index c3c0903..97c804a 100644
--- a/tests/async/test_server.py
+++ b/tests/async/test_server.py
@@ -937,7 +937,7 @@ class TestAsyncServer:
         await s.disconnect('1', namespace='/foo')
         assert calls == s.eio.send.await_count
 
-    async def test_disconnect_with_partial_binary_packet(self, eio):
+    async def test_server_disconnect_with_partial_binary_packet(self, eio):
         eio.return_value.send = mock.AsyncMock()
         eio.return_value.disconnect = mock.AsyncMock()
         s = async_server.AsyncServer()
@@ -955,6 +955,23 @@ class TestAsyncServer:
         s.eio.send.assert_any_await('123', '1')
         assert '123' not in s._binary_packet
 
+    async def test_client_disconnect_with_partial_binary_packet(self, eio):
+        eio.return_value.send = mock.AsyncMock()
+        eio.return_value.disconnect = mock.AsyncMock()
+        s = async_server.AsyncServer()
+        await s._handle_eio_connect('123', 'environ')
+        await s._handle_eio_message('123', '0')
+        await s._handle_eio_message(
+            '123',
+            '52-["my message","a",'
+            '{"_placeholder":true,"num":1},'
+            '{"_placeholder":true,"num":0}]',
+        )
+        await s._handle_eio_message('123', b'foo')
+        assert s._binary_packet['123'] is not None
+        await s._handle_disconnect('123', '/')
+        assert '123' not in s._binary_packet
+
     async def test_namespace_handler(self, eio):
         eio.return_value.send = mock.AsyncMock()
         result = {}
diff --git a/tests/common/test_server.py b/tests/common/test_server.py
index d8d80dc..251d661 100644
--- a/tests/common/test_server.py
+++ b/tests/common/test_server.py
@@ -862,7 +862,7 @@ class TestServer:
         s.disconnect('123', namespace='/foo')
         assert calls == s.eio.send.call_count
 
-    def test_disconnect_with_partial_binary_packet(self, eio):
+    def test_disconnect_server_with_partial_binary_packet(self, eio):
         s = server.Server()
         s._handle_eio_connect('123', 'environ')
         s._handle_eio_message('123', '0')
@@ -878,6 +878,21 @@ class TestServer:
         s.eio.send.assert_any_call('123', '1')
         assert '123' not in s._binary_packet
 
+    def test_disconnect_client_with_partial_binary_packet(self, eio):
+        s = server.Server()
+        s._handle_eio_connect('123', 'environ')
+        s._handle_eio_message('123', '0')
+        s._handle_eio_message(
+            '123',
+            '52-["my message","a",'
+            '{"_placeholder":true,"num":1},'
+            '{"_placeholder":true,"num":0}]',
+        )
+        s._handle_eio_message('123', b'foo')
+        assert s._binary_packet['123'] is not None
+        s._handle_disconnect('123', '/')
+        assert '123' not in s._binary_packet
+
     def test_namespace_handler(self, eio):
         result = {}