diff --git a/ChangeLog b/ChangeLog
index ec0d901..904cb20 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,7 +1,8 @@
-2003-02-21  Bruno Haible  <bruno@clisp.org>
+2003-02-24  Bruno Haible  <bruno@clisp.org>
 
 	* src/base/random/cl_random_from.cc (random_state::random_state): Add
 	support for MacOS X.
+	* src/modinteger/cl_MI.cc: #undef _R.
 	Reported by Erann Gat <gat@jpl.nasa.gov>.
 
 2002-08-03  Joerg Arndt  <jj@suse.de>
diff --git a/src/modinteger/cl_MI.cc b/src/modinteger/cl_MI.cc
index 3aae64d..6be4179 100644
--- a/src/modinteger/cl_MI.cc
+++ b/src/modinteger/cl_MI.cc
@@ -21,6 +21,10 @@ CL_PROVIDE(cl_MI)
 #include "cln/abort.h"
 #include "cl_alloca.h"
 
+# MacOS X does "#define _R 0x00040000L"
+# Grr...
+#undef _R
+
 namespace cln {
 
 cl_heap_modint_ring::cl_heap_modint_ring (cl_I m, cl_modint_setops* setopv, cl_modint_addops* addopv, cl_modint_mulops* mulopv)