diff --git a/artiq/protocols/sync_struct.py b/artiq/protocols/sync_struct.py
index 039fb2ac4..3d64450da 100644
--- a/artiq/protocols/sync_struct.py
+++ b/artiq/protocols/sync_struct.py
@@ -63,7 +63,7 @@ class Subscriber:
 
     async def connect(self, host, port, before_receive_cb=None):
         self.reader, self.writer = \
-            await asyncio.open_connection(host, port)
+            await asyncio.open_connection(host, port, limit=4*1024*1024)
         try:
             if before_receive_cb is not None:
                 before_receive_cb()