diff --git a/swiftmpistepsim2.c b/swiftmpistepsim2.c
index c775c7ce70be9034393b912ce8918244f999ca10..6efbb8d9bdf1f31638e7c6496ceb58633751a2d7 100644
--- a/swiftmpistepsim2.c
+++ b/swiftmpistepsim2.c
@@ -17,6 +17,8 @@
  *
  ******************************************************************************/
 
+/* Variation that uses a synchronous MPI_Send. */
+
 #include <limits.h>
 #include <mpi.h>
 #include <pthread.h>