diff --git a/modules/client/sync.cc b/modules/client/sync.cc
index ee340f64b..0261805c1 100644
--- a/modules/client/sync.cc
+++ b/modules/client/sync.cc
@@ -558,6 +558,9 @@ try
 		if(!dock.wait_until(args.timesout))
 			break;
 
+		assert(data.client && data.client->sock);
+		check(*data.client->sock);
+
 		if(queue.empty())
 			continue;
 
@@ -582,6 +585,17 @@ try
 
 	return false;
 }
+catch(const std::system_error &e)
+{
+	log::derror
+	{
+		log, "longpoll %s failed :%s",
+		loghead(data),
+		e.what()
+	};
+
+	throw;
+}
 catch(const std::exception &e)
 {
 	log::error