diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 815d637a3..ebca081f8 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,7 @@
+Thu Oct  5  1:13:00 2000  Corinna Vinschen <corinna@vinschen.de>
+
+	* include/sys/mman.h: Add missing MAP_FAILED macro.
+
 Wed Oct  4 18:48:00 2000  Corinna Vinschen <corinna@vinschen.de>
 
 	* fhandler.h (fhandler_dev_mem): Add method `init'. Add members
diff --git a/winsup/cygwin/include/sys/mman.h b/winsup/cygwin/include/sys/mman.h
index 9f36bc323..244dcdb39 100644
--- a/winsup/cygwin/include/sys/mman.h
+++ b/winsup/cygwin/include/sys/mman.h
@@ -21,6 +21,8 @@ extern "C" {
 #define MAP_ANONYMOUS 0x20
 #define MAP_ANON MAP_ANONYMOUS
 
+#define MAP_FAILED ((caddr_t)-1)
+
 /*
  * Flags for msync.
  */