diff --git a/lib/types.nix b/lib/types.nix
index 4d6ac51c8988..46030dea7263 100644
--- a/lib/types.nix
+++ b/lib/types.nix
@@ -349,6 +349,16 @@ rec {
       functor = (defaultFunctor name) // { wrapped = elemType; };
     };
 
+    functionTo = elemType: mkOptionType {
+      name = "function that evaluates to a(n) ${elemType.name}";
+      check = isFunction;
+      merge = loc: defs:
+        fnArgs: elemType.merge loc (map (fn: { inherit (fn) file; value = fn.value fnArgs; }) defs);
+      getSubOptions = elemType.getSubOptions;
+      getSubModules = elemType.getSubModules;
+      substSubModules = m: functionTo (elemType.substSubModules m);
+    };
+
     # A submodule (like typed attribute set). See NixOS manual.
     submodule = opts:
       let