diff --git a/installer/nixos-rebuild.sh b/installer/nixos-rebuild.sh
index 0552c9baaf0..33639daa568 100644
--- a/installer/nixos-rebuild.sh
+++ b/installer/nixos-rebuild.sh
@@ -28,6 +28,19 @@ if test -z "$NIXOS"; then NIXOS=/etc/nixos/nixos; fi
 if test -z "$NIXOS_CONFIG"; then NIXOS_CONFIG=/etc/nixos/configuration.nix; fi
 
 
+# Pull the manifests defined in the configuration (the "manifests"
+# attribute).  Wonderfully hacky.
+manifests=$(nix-instantiate --eval-only --xml --strict \
+    $NIXOS/system/system.nix \
+    --arg configuration "import $NIXOS_CONFIG" \
+    -A manifests \
+    | grep '<string'  | sed 's^.*"\(.*\)".*^\1^g')
+    
+for i in $manifests; do
+    NIX_DOWNLOAD_CACHE=/nix/var/nix/channel-cache nix-pull $i || true
+done
+
+
 # Either upgrade the configuration in the system profile (for "switch"
 # or "boot"), or just build it and create a symlink "result" in the
 # current directory (for "build" and "test").
diff --git a/system/options.nix b/system/options.nix
index bc694312231..04965de59f0 100644
--- a/system/options.nix
+++ b/system/options.nix
@@ -909,6 +909,20 @@
   }
 
   
+  {
+    name = ["installer" "manifests"];
+    default = [http://nix.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable/MANIFEST];
+    example =
+      [ http://nix.cs.uu.nl/dist/nix/channels-v3/nixpkgs-unstable/MANIFEST
+        http://nix.cs.uu.nl/dist/nix/channels-v3/nixpkgs-stable/MANIFEST
+      ];
+    description = "
+      URLs of manifests to be downloaded when you run
+      <command>nixos-rebuild</command> to speed up builds.
+    ";
+  }
+
+  
   {
     name = ["nix" "maxJobs"];
     default = 1;
diff --git a/system/system.nix b/system/system.nix
index a2a677d8e47..d8d7d6e85ab 100644
--- a/system/system.nix
+++ b/system/system.nix
@@ -27,6 +27,8 @@ rec {
     allPackages = import ../pkgs/top-level/all-packages.nix;
   };
 
+  manifests = config.get ["installer" "manifests"]; # exported here because nixos-rebuild uses it
+
   nix = pkgs.nixUnstable; # we need the exportReferencesGraph feature
 
   useKernel = (config.get ["boot" "useKernel"]) pkgs;
diff --git a/upstart-jobs/ifplugd.nix b/upstart-jobs/ifplugd.nix
index b3f4b811c33..a1b755a7ad6 100644
--- a/upstart-jobs/ifplugd.nix
+++ b/upstart-jobs/ifplugd.nix
@@ -10,6 +10,7 @@ let
   plugScript = writeScript "ifplugd.action" "#! ${bash}/bin/sh
     if test \"$2\" = up; then
       initctl stop dhclient
+      sleep 1
       initctl start dhclient
     fi
   ";