diff --git a/lib/fluent/plugin/in_forward.rb b/lib/fluent/plugin/in_forward.rb
index <HASH>..<HASH> 100644
--- a/lib/fluent/plugin/in_forward.rb
+++ b/lib/fluent/plugin/in_forward.rb
@@ -200,7 +200,7 @@ class ForwardInput < Input
 
   def on_heartbeat_request(host, port, msg)
     #$log.trace "heartbeat request from #{host}:#{port}"
-    @usock.send msg, 0, host, port
+    @usock.send "", 0, host, port
   end
 end
 
diff --git a/lib/fluent/plugin/out_forward.rb b/lib/fluent/plugin/out_forward.rb
index <HASH>..<HASH> 100644
--- a/lib/fluent/plugin/out_forward.rb
+++ b/lib/fluent/plugin/out_forward.rb
@@ -334,7 +334,7 @@ class ForwardOutput < ObjectBufferedOutput
       else
         now = Engine.now
         rh = @resolved_host
-        if !rh || (@dns_cache_expire && now - @resolved_time >= @dns_cache_expire)
+        if !rh || now - @resolved_time >= @dns_cache_expire
           rh = @resolved_host = resolve_dns!
           @resolved_time = now
         end
out_forward: reverted on_heartbeat_request not to return received msg [#<I>]