diff --git a/socketio/asyncio_server.py b/socketio/asyncio_server.py
index 251d581..92f1a8d 100644
--- a/socketio/asyncio_server.py
+++ b/socketio/asyncio_server.py
@@ -360,8 +360,10 @@ class AsyncServer(server.Server):
         # as a single argument
         if isinstance(data, tuple):
             data = list(data)
-        else:
+        elif data is not None:
             data = [data]
+        else:
+            data = []
         await self._send_packet(sid, packet.Packet(
             packet.EVENT, namespace=namespace, data=[event] + data, id=id,
             binary=None))
diff --git a/socketio/server.py b/socketio/server.py
index 76b7d2e..3327e4d 100644
--- a/socketio/server.py
+++ b/socketio/server.py
@@ -570,8 +570,10 @@ class Server(object):
         # as a single argument
         if isinstance(data, tuple):
             data = list(data)
-        else:
+        elif data is not None:
             data = [data]
+        else:
+            data = []
         self._send_packet(sid, packet.Packet(packet.EVENT, namespace=namespace,
                                              data=[event] + data, id=id,
                                              binary=binary))