diff --git a/src/ChangeLog b/src/ChangeLog
index f5ee64b2..cf6d5275 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2001-06-14  Hrvoje Niksic  <hniksic@arsdigita.com>
+
+	* sysdep.h (MAP_FAILED): Provide MAP_FAILED for systems that don't
+	define it.
+
 2001-06-09  Jan Prikryl  <prikryl@cg.tuwien.ac.at>
 
 	* ftp.h: Provide correct prototype for ftp_parse_ls().
diff --git a/src/sysdep.h b/src/sysdep.h
index 52db05da..6568980a 100644
--- a/src/sysdep.h
+++ b/src/sysdep.h
@@ -178,4 +178,14 @@ void *memcpy ();
 #endif /* sun */
 #endif /* STDC_HEADERS */
 
+/* Some systems don't provide MAP_FAILED, a symbolic constant for the
+   value returned by mmap() when it doesn't work.  Usually, this
+   constant should be -1.  This only makes sense for files that use
+   mmap() and include sys/mman.h *before* sysdep.h, but doesn't hurt
+   others.  */
+
+#ifndef MAP_FAILED
+# define MAP_FAILED ((void *) -1)
+#endif
+
 #endif /* SYSDEP_H */