diff --git a/lib/types.nix b/lib/types.nix
index afc8f80eb0e..ac84ef29611 100644
--- a/lib/types.nix
+++ b/lib/types.nix
@@ -195,6 +195,25 @@ rec {
             args = { name = ""; }; }).options;
       };
 
+    nixosSubmodule = nixos: args: mkOptionType rec {
+      name = "submodule containing a NixOS config";
+      check = x: isAttrs x || isFunction x;
+      merge = loc: defs:
+        let
+          coerce = def: if isFunction def then def else { config = def; };
+        in (import (nixos + "/lib/eval-config.nix") (args // {
+          modules = (args.modules or []) ++
+            map (def: { _file = def.file; imports = [(coerce def.value)]; }) defs;
+
+          prefix = loc;
+        })).config;
+      getSubOptions = prefix: (import (nixos + "/lib/eval-config.nix") (args // {
+        modules = (args.modules or []);
+
+        inherit prefix;
+      })).options;
+    };
+
     # Obsolete alternative to configOf.  It takes its option
     # declarations from the ‘options’ attribute of containing option
     # declaration.
diff --git a/nixos/modules/virtualisation/containers.nix b/nixos/modules/virtualisation/containers.nix
index bcbfaacd703..531ee559663 100644
--- a/nixos/modules/virtualisation/containers.nix
+++ b/nixos/modules/virtualisation/containers.nix
@@ -15,6 +15,7 @@ with pkgs.lib;
     };
 
     systemd.containers = mkOption {
+      # !!! Should probably use nixosSubmodule here
       type = types.attrsOf (types.submodule (
         { config, options, name, ... }:
         {
@@ -134,4 +135,4 @@ with pkgs.lib;
       }) config.systemd.containers;
 
   };
-}
\ No newline at end of file
+}