face: send and receive NACK

refs #2930

Change-Id: I70c969ac12b493d2c83fa892beffae936cc23791
diff --git a/src/lp/packet.hpp b/src/lp/packet.hpp
index 53b998d..eed6b51 100644
--- a/src/lp/packet.hpp
+++ b/src/lp/packet.hpp
@@ -55,7 +55,7 @@
   /**
    * \brief encode packet into wire format
    */
-  const Block&
+  const Block
   wireEncode() const;
 
   /**