diff --git a/common/MPI_Helpers.h b/common/MPI_Helpers.h
index 02d67732..fde70618 100644
--- a/common/MPI_Helpers.h
+++ b/common/MPI_Helpers.h
@@ -18,6 +18,7 @@
     #define MPI_COMM_WORLD 0
     #define MPI_COMM_SELF 0
     #define MPI_COMM_NULL -1
+    #define MPI_GROUP_NULL -2
     #define MPI_STATUS_IGNORE NULL
     enum MPI_Datatype { MPI_LOGICAL, MPI_CHAR, MPI_UNSIGNED_CHAR, MPI_INT, 
         MPI_UNSIGNED, MPI_LONG, MPI_UNSIGNED_LONG, MPI_LONG_LONG, MPI_FLOAT, MPI_DOUBLE };