Index: head/sys/compat/freebsd32/syscalls.master
===================================================================
--- head/sys/compat/freebsd32/syscalls.master
+++ head/sys/compat/freebsd32/syscalls.master
@@ -388,7 +388,7 @@
 				    uint32_t length1, uint32_t length2); }
 202	AUE_SYSCTL	STD	{ int freebsd32___sysctl(int *name, \
 				    u_int namelen, void *old, \
-				    uint32_t *oldlenp, void *new, \
+				    uint32_t *oldlenp, const void *new, \
 				    uint32_t newlen); }
 203	AUE_MLOCK	NOPROTO	{ int mlock(const void *addr, \
 				    size_t len); }
Index: head/sys/kern/kern_sysctl.c
===================================================================
--- head/sys/kern/kern_sysctl.c
+++ head/sys/kern/kern_sysctl.c
@@ -1772,7 +1772,7 @@
 		return (0);
 	if (req->newlen - req->newidx < l)
 		return (EINVAL);
-	bcopy((char *)req->newptr + req->newidx, p, l);
+	bcopy((const char *)req->newptr + req->newidx, p, l);
 	req->newidx += l;
 	return (0);
 }
@@ -1898,7 +1898,7 @@
 		return (EINVAL);
 	WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL,
 	    "sysctl_new_user()");
-	error = copyin((char *)req->newptr + req->newidx, p, l);
+	error = copyin((const char *)req->newptr + req->newidx, p, l);
 	req->newidx += l;
 	return (error);
 }
@@ -2126,8 +2126,8 @@
  */
 int
 userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
-    size_t *oldlenp, int inkernel, void *new, size_t newlen, size_t *retval,
-    int flags)
+    size_t *oldlenp, int inkernel, const void *new, size_t newlen,
+    size_t *retval, int flags)
 {
 	int error = 0, memlocked;
 	struct sysctl_req req;
Index: head/sys/kern/syscalls.master
===================================================================
--- head/sys/kern/syscalls.master
+++ head/sys/kern/syscalls.master
@@ -1209,7 +1209,7 @@
 		    u_int namelen,
 		    _Out_writes_bytes_opt_(*oldlenp) void *old,
 		    _Inout_opt_ size_t *oldlenp,
-		    _In_reads_bytes_opt_(newlen) void *new,
+		    _In_reads_bytes_opt_(newlen) const void *new,
 		    size_t newlen
 		);
 	} __sysctl sysctl_args int
Index: head/sys/sys/sysctl.h
===================================================================
--- head/sys/sys/sysctl.h
+++ head/sys/sys/sysctl.h
@@ -165,7 +165,7 @@
 	size_t		 oldlen;
 	size_t		 oldidx;
 	int		(*oldfunc)(struct sysctl_req *, const void *, size_t);
-	void		*newptr;
+	const void		*newptr;
 	size_t		 newlen;
 	size_t		 newidx;
 	int		(*newfunc)(struct sysctl_req *, void *, size_t);
@@ -1083,7 +1083,7 @@
 	    size_t *oldlenp, void *new, size_t newlen, size_t *retval,
 	    int flags);
 int	userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
-	    size_t *oldlenp, int inkernel, void *new, size_t newlen,
+	    size_t *oldlenp, int inkernel, const void *new, size_t newlen,
 	    size_t *retval, int flags);
 int	sysctl_find_oid(int *name, u_int namelen, struct sysctl_oid **noid,
 	    int *nindx, struct sysctl_req *req);