diff --git a/go/ssa/interp/external_darwin.go b/go/ssa/interp/external_darwin.go
new file mode 100644
index 00000000..4974ad60
--- /dev/null
+++ b/go/ssa/interp/external_darwin.go
@@ -0,0 +1,18 @@
+// Copyright 2014 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.
+
+// +build darwin
+
+package interp
+
+import "syscall"
+
+func init() {
+	externals["syscall.Sysctl"] = ext۰syscall۰Sysctl
+}
+
+func ext۰syscall۰Sysctl(fr *frame, args []value) value {
+	r, err := syscall.Sysctl(args[0].(string))
+	return tuple{r, wrapError(err)}
+}