diff --git a/newlib/libc/sys/rtems/include/sys/mman.h b/newlib/libc/sys/rtems/include/sys/mman.h
index 8aeed87bc..c099e2242 100644
--- a/newlib/libc/sys/rtems/include/sys/mman.h
+++ b/newlib/libc/sys/rtems/include/sys/mman.h
@@ -90,6 +90,7 @@
 /*
  * Extended flags
  */
+#define	MAP_GUARD	 0x00002000 /* reserve but don't map address range */
 #define	MAP_EXCL	 0x00004000 /* for MAP_FIXED, fail if address is used */
 #define	MAP_NOCORE	 0x00020000 /* dont include these pages in a coredump */
 #define	MAP_PREFAULT_READ 0x00040000 /* prefault mapping for reading */