diff --git a/mtest/mpi.c b/mtest/mpi.c
index 47083a3..95c3811 100644
--- a/mtest/mpi.c
+++ b/mtest/mpi.c
@@ -2,10 +2,12 @@
     mpi.c
 
     by Michael J. Fromberger <sting@linguist.dartmouth.edu>
-    Copyright (C) 1998 Michael J. Fromberger, All Rights Reserved
+    Copyright (C) 1998 Michael J. Fromberger
 
     Arbitrary precision integer arithmetic library
 
+    SPDX-License-Identifier: Unlicense
+
     $Id$
  */
 
diff --git a/mtest/mpi.h b/mtest/mpi.h
index 5accb52..9a9cc41 100644
--- a/mtest/mpi.h
+++ b/mtest/mpi.h
@@ -2,10 +2,12 @@
     mpi.h
 
     by Michael J. Fromberger <sting@linguist.dartmouth.edu>
-    Copyright (C) 1998 Michael J. Fromberger, All Rights Reserved
+    Copyright (C) 1998 Michael J. Fromberger
 
     Arbitrary precision integer arithmetic library
 
+    SPDX-License-Identifier: Unlicense
+
     $Id$
  */