diff --git a/lib/fluent/plugin/out_keep_forward.rb b/lib/fluent/plugin/out_keep_forward.rb
index 9792b48..1cadad9 100644
--- a/lib/fluent/plugin/out_keep_forward.rb
+++ b/lib/fluent/plugin/out_keep_forward.rb
@@ -200,6 +200,9 @@ def reconnect(node)
   end
 
   def sock_write(sock, tag, chunk)
+    oldsync = sock.sync
+    sock.sync = false
+
     # beginArray(2)
     sock.write FORWARD_HEADER
 
@@ -221,6 +224,10 @@ def sock_write(sock, tag, chunk)
 
     # writeRawBody(packed_es)
     chunk.write_to(sock)
+
+  ensure
+    sock.sync = oldsync
+    sock.flush # for immediate call of write(2)
   end
 
   # watcher thread callback