diff --git a/route/syscall.go b/route/syscall.go
index 97166dd..68d37c9 100644
--- a/route/syscall.go
+++ b/route/syscall.go
@@ -2,28 +2,12 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build dragonfly || freebsd || netbsd || openbsd
-// +build dragonfly freebsd netbsd openbsd
+//go:build darwin || dragonfly || freebsd || netbsd || openbsd
+// +build darwin dragonfly freebsd netbsd openbsd
 
 package route
 
-import (
-	"syscall"
-	"unsafe"
-)
+import _ "unsafe" // for linkname
 
-var zero uintptr
-
-func sysctl(mib []int32, old *byte, oldlen *uintptr, new *byte, newlen uintptr) error {
-	var p unsafe.Pointer
-	if len(mib) > 0 {
-		p = unsafe.Pointer(&mib[0])
-	} else {
-		p = unsafe.Pointer(&zero)
-	}
-	_, _, errno := syscall.Syscall6(syscall.SYS___SYSCTL, uintptr(p), uintptr(len(mib)), uintptr(unsafe.Pointer(old)), uintptr(unsafe.Pointer(oldlen)), uintptr(unsafe.Pointer(new)), newlen)
-	if errno != 0 {
-		return error(errno)
-	}
-	return nil
-}
+//go:linkname sysctl syscall.sysctl
+func sysctl(mib []int32, old *byte, oldlen *uintptr, new *byte, newlen uintptr) error
diff --git a/route/syscall_go1_12_darwin.go b/route/syscall_go1_12_darwin.go
deleted file mode 100644
index 7a13e4f..0000000
--- a/route/syscall_go1_12_darwin.go
+++ /dev/null
@@ -1,13 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-//go:build go1.12
-// +build go1.12
-
-package route
-
-import _ "unsafe" // for linkname
-
-//go:linkname sysctl syscall.sysctl
-func sysctl(mib []int32, old *byte, oldlen *uintptr, new *byte, newlen uintptr) error