diff --git a/newlib/libc/sys/rtems/include/sys/mman.h b/newlib/libc/sys/rtems/include/sys/mman.h
index 6c757c8ba..a13e3d161 100644
--- a/newlib/libc/sys/rtems/include/sys/mman.h
+++ b/newlib/libc/sys/rtems/include/sys/mman.h
@@ -89,6 +89,7 @@
 /*
  * Extended flags
  */
+#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 */
 #ifdef __LP64__