diff --git a/doc/mpi.qbk b/doc/mpi.qbk
index bacb266..5268f3d 100644
--- a/doc/mpi.qbk
+++ b/doc/mpi.qbk
@@ -110,7 +110,7 @@ prints a message to standard output.
   #include <mpi.h>
   #include <iostream>
 
-  int main()
+  int main(int argc, char* argv[])
   {
     MPI_Init(&argc, &argv);