diff --git a/aclocal/ax_thrift_internal.m4 b/aclocal/ax_thrift_internal.m4
index 9348f4a..979bec6 100644
--- a/aclocal/ax_thrift_internal.m4
+++ b/aclocal/ax_thrift_internal.m4
@@ -9,6 +9,11 @@
 dnl
 dnl @version 2008-02-20
 dnl @license AllPermissive
+dnl
+dnl Copyright (C) 2009 David Reiss
+dnl Copying and distribution of this file, with or without modification,
+dnl are permitted in any medium without royalty provided the copyright
+dnl notice and this notice are preserved.
 
 AC_DEFUN([AX_THRIFT_GEN],
          [