diff --git a/src/wsdd.py b/src/wsdd.py
index 7d66571..9a2de38 100755
--- a/src/wsdd.py
+++ b/src/wsdd.py
@@ -1123,6 +1123,7 @@ def do_POST(self) -> None:
 class ApiServer:
 
     address_monitor: 'NetworkAddressMonitor'
+    clients: List[asyncio.StreamWriter]
 
     def __init__(self, aio_loop: asyncio.AbstractEventLoop, listen_address: bytes,
                  address_monitor: 'NetworkAddressMonitor') -> None: