--- a/src/mpi/model/null-message-mpi-interface.cc	Sun Feb 23 13:49:13 2014 -0800
+++ b/src/mpi/model/null-message-mpi-interface.cc	Tue Feb 25 12:27:05 2014 -0500
@@ -49,8 +49,9 @@
  * maximum MPI message size for easy
  * buffer creation
  */
+#ifdef NS3_MPI
 const uint32_t NULL_MESSAGE_MAX_MPI_MSG_SIZE = 2000;
-
+#endif
 
 NullMessageSentBuffer::NullMessageSentBuffer ()
 {