diff --git a/lib/mpi/mpiutil.c b/lib/mpi/mpiutil.c
index eefc55d..6bfc41f 100644
--- a/lib/mpi/mpiutil.c
+++ b/lib/mpi/mpiutil.c
@@ -135,7 +135,7 @@
 	size_t i;
 	MPI b;
 
-	*copied = MPI_NULL;
+	*copied = NULL;
 
 	if (a) {
 		b = mpi_alloc(a->nlimbs);