diff --git a/src/include/unistd.h b/src/include/unistd.h
index e8fe19b2..050ec914 100644
--- a/src/include/unistd.h
+++ b/src/include/unistd.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: unistd.h,v 1.29 2000/01/27 05:18:47 itojun Exp $ */
+/*	$OpenBSD: unistd.h,v 1.30 2000/02/19 13:21:25 deraadt Exp $ */
 /*	$NetBSD: unistd.h,v 1.26.4.1 1996/05/28 02:31:51 mrg Exp $	*/
 
 /*-
@@ -185,7 +185,7 @@ int	 setruid __P((uid_t));
 void	 setusershell __P((void));
 void	 swab __P((const void *, void *, size_t));
 int	 swapon __P((const char *));
-int	 swapctl __P((int cmd, void *arg, int misc));
+int	 swapctl __P((int cmd, const void *arg, int misc));
 int	 symlink __P((const char *, const char *));
 void	 sync __P((void));
 int	 syscall __P((int, ...));