diff --git a/config.ml b/config.ml
index f28928e..c092574 100644
--- a/config.ml
+++ b/config.ml
@@ -1,3 +1,4 @@
+(* mirage >= 4.5.0 *)
 (* Copyright (C) 2017, Thomas Leonard <thomas.leonard@unikernel.com>
    See the README file for details. *)
 
@@ -5,55 +6,31 @@
 
 open Mirage
 
-let table_size =
-  let info = Key.Arg.info
-      ~doc:"The number of NAT entries to allocate."
-      ~docv:"ENTRIES" ["nat-table-size"]
-  in
-  let key = Key.Arg.opt ~stage:`Both Key.Arg.int 5_000 info in
-  Key.create "nat_table_size" key
-
-let ipv4 =
-  let doc = Key.Arg.info ~doc:"Manual IP setting." ["ipv4"] in
-  Key.(create "ipv4" Arg.(opt string "0.0.0.0" doc))
-
-let ipv4_gw =
-  let doc = Key.Arg.info ~doc:"Manual Gateway IP setting." ["ipv4-gw"] in
-  Key.(create "ipv4_gw" Arg.(opt string "0.0.0.0" doc))
-
-let ipv4_dns =
-  let doc = Key.Arg.info ~doc:"Manual DNS IP setting." ["ipv4-dns"] in
-  Key.(create "ipv4_dns" Arg.(opt string "10.139.1.1" doc))
-
-let ipv4_dns2 =
-  let doc = Key.Arg.info ~doc:"Manual Second DNS IP setting." ["ipv4-dns2"] in
-  Key.(create "ipv4_dns2" Arg.(opt string "10.139.1.2" doc))
+let nat_table_size = runtime_arg ~pos:__POS__ "Unikernel.nat_table_size"
+let ipv4 = runtime_arg ~pos:__POS__ "Unikernel.ipv4"
+let ipv4_gw = runtime_arg ~pos:__POS__ "Unikernel.ipv4_gw"
+let ipv4_dns = runtime_arg ~pos:__POS__ "Unikernel.ipv4_dns"
+let ipv4_dns2 = runtime_arg ~pos:__POS__ "Unikernel.ipv4_dns2"
 
 let main =
-  foreign
-    ~keys:[
-      Key.v table_size;
-      Key.v ipv4;
-      Key.v ipv4_gw;
-      Key.v ipv4_dns;
-      Key.v ipv4_dns2;
-    ]
+   main
+    ~runtime_args:[ nat_table_size; ]
     ~packages:[
       package "vchan" ~min:"4.0.2";
       package "cstruct";
       package "astring";
       package "tcpip" ~min:"3.7.0";
-      package ~min:"2.3.0" ~sublibs:["mirage"] "arp";
-      package ~min:"3.0.0" "ethernet";
+      package "arp" ~min:"2.3.0" ~sublibs:["mirage"];
+      package "ethernet" ~min:"3.0.0";
       package "shared-memory-ring" ~min:"3.0.0";
-      package ~min:"2.1.3" "netchannel";
-      package ~min:"2.1.3" "mirage-net-xen";
+      package "netchannel" ~min:"2.1.3";
+      package "mirage-net-xen" ~min:"2.1.3";
       package "ipaddr" ~min:"5.2.0";
       package "mirage-qubes" ~min:"0.9.1";
-      package ~min:"3.0.1" "mirage-nat";
+      package "mirage-nat" ~min:"3.0.1";
       package "mirage-logs";
       package "mirage-xen" ~min:"8.0.0";
-      package ~min:"6.4.0" "dns-client";
+      package "dns-client" ~min:"6.4.0";
       package "pf-qubes";
     ]
     "Unikernel.Main" (random @-> mclock @-> time @-> job)
diff --git a/fw_utils.ml b/fw_utils.ml
index 4469e4d..0307810 100644
--- a/fw_utils.ml
+++ b/fw_utils.ml
@@ -8,7 +8,7 @@ module IpMap = struct
   let find x map =
     try Some (find x map)
     with Not_found -> None
-    | e -> Logs.err( fun f -> f "uncaught exception in find...%!"); None
+    | _ -> Logs.err( fun f -> f "uncaught exception in find...%!"); None
 end
 
 (** An Ethernet interface. *)
diff --git a/unikernel.ml b/unikernel.ml
index ef02620..dcbdafe 100644
--- a/unikernel.ml
+++ b/unikernel.ml
@@ -3,10 +3,31 @@
 
 open Lwt
 open Qubes
+open Cmdliner
 
 let src = Logs.Src.create "unikernel" ~doc:"Main unikernel code"
 module Log = (val Logs.src_log src : Logs.LOG)
 
+let nat_table_size =
+  let doc = Arg.info ~doc:"The number of NAT entries to allocate." [ "nat-table-size" ] in
+  Arg.(value & opt int 5_000 doc)
+
+let ipv4 =
+  let doc = Arg.info ~doc:"Manual IP setting." [ "ipv4" ] in
+  Arg.(value & opt string "0.0.0.0" doc)
+
+let ipv4_gw =
+  let doc = Arg.info ~doc:"Manual Gateway IP setting." [ "ipv4-gw" ] in
+  Arg.(value & opt string "0.0.0.0" doc)
+
+let ipv4_dns =
+  let doc = Arg.info ~doc:"Manual DNS IP setting." [ "ipv4-dns" ] in
+  Arg.(value & opt string "10.139.1.1" doc)
+
+let ipv4_dns2 =
+  let doc = Arg.info ~doc:"Manual Second DNS IP setting." [ "ipv4-dns2" ] in
+  Arg.(value & opt string "10.139.1.2" doc)
+
 module Main (R : Mirage_random.S)(Clock : Mirage_clock.MCLOCK)(Time : Mirage_time.S) = struct
   module Dispatcher = Dispatcher.Make(R)(Clock)(Time)
   module Dns_transport = My_dns.Transport(R)(Clock)(Time)
@@ -24,7 +45,7 @@ module Main (R : Mirage_random.S)(Clock : Mirage_clock.MCLOCK)(Time : Mirage_tim
     ]
 
   (* Main unikernel entry point (called from auto-generated main.ml). *)
-  let start _random _clock _time =
+  let start _random _clock _time nat_table_size ipv4 ipv4_gw ipv4_dns ipv4_dns2 =
     let start_time = Clock.elapsed_ns () in
     (* Start qrexec agent and QubesDB agent in parallel *)
     let qrexec = RExec.connect ~domid:0 () in
@@ -45,13 +66,12 @@ module Main (R : Mirage_random.S)(Clock : Mirage_clock.MCLOCK)(Time : Mirage_tim
       Xen_os.Lifecycle.await_shutdown_request () >>= fun (`Poweroff | `Reboot) ->
       Lwt.return_unit in
     (* Set up networking *)
-    let max_entries = Key_gen.nat_table_size () in
-    let nat = My_nat.create ~max_entries in
+    let nat = My_nat.create ~max_entries:nat_table_size in
 
-    let netvm_ip = Ipaddr.V4.of_string_exn (Key_gen.ipv4_gw ()) in
-    let our_ip = Ipaddr.V4.of_string_exn (Key_gen.ipv4 ()) in
-    let dns = Ipaddr.V4.of_string_exn (Key_gen.ipv4_dns ()) in
-    let dns2 = Ipaddr.V4.of_string_exn (Key_gen.ipv4_dns2 ()) in
+    let netvm_ip = Ipaddr.V4.of_string_exn ipv4_gw in
+    let our_ip = Ipaddr.V4.of_string_exn ipv4 in
+    let dns = Ipaddr.V4.of_string_exn ipv4_dns in
+    let dns2 = Ipaddr.V4.of_string_exn ipv4_dns2 in
     
     let zero_ip = (Ipaddr.V4.make 0 0 0 0) in