diff --git a/pkgs/lib/modules.nix b/pkgs/lib/modules.nix
index 286178a0fa70..ea38010ceccc 100644
--- a/pkgs/lib/modules.nix
+++ b/pkgs/lib/modules.nix
@@ -75,12 +75,19 @@ rec {
         );
 
 
-  unifyOptionModule = {key ? "<unknown location>"}: m: (args:
-    let module = lib.applyIfFunction m args; in
-    if lib.isModule module then
-      { inherit key; } // module
+  unifyOptionModule = {key ? "<unknown location>"}: name: index: m: (args:
+    let
+      module = lib.applyIfFunction m args;
+      key_ = rec {
+        file = key;
+        option = name;
+        number = index;
+        outPath = key;
+      };
+    in if lib.isModule module then
+      { key = key_; } // module
     else
-      { inherit key; options = module; }
+      { key = key_; options = module; }
   );
 
 
@@ -197,9 +204,9 @@ rec {
       recurseInto = name:
         moduleMerge (addName name) (modulesOf name);
 
-      recurseForOption = name: modules:
+      recurseForOption = name: modules: args:
         moduleMerge name (
-          map unifyModuleSyntax modules
+          moduleClosure modules args
         );
 
       errorSource = modules:
@@ -240,7 +247,7 @@ rec {
           decls = # add location to sub-module options.
             map (m:
               mapSubOptions
-                (unifyOptionModule {inherit (m) key;})
+                (unifyOptionModule {inherit (m) key;} name)
                 m.options
             ) declarations;
 
diff --git a/pkgs/lib/options.nix b/pkgs/lib/options.nix
index 3a8cc0006ef1..1fdf9ad8088d 100644
--- a/pkgs/lib/options.nix
+++ b/pkgs/lib/options.nix
@@ -31,7 +31,7 @@ rec {
   mapSubOptions = f: opt:
     if opt ? options then
       opt // {
-        options = map f (toList opt.options);
+        options = imap f (toList opt.options);
       }
     else
       opt;
@@ -82,16 +82,18 @@ rec {
       handleOptionSets = opt:
         if opt ? type && opt.type.hasOptions then
           let
-            
-            optionConfig = vals: args:
-              map (f: lib.applyIfFunction f args)
-                (opt.options ++ toList vals);
-
             # Evaluate sub-modules.
             subModuleMerge = path: vals:
               lib.fix (args:
                 let
-                  result = recurseInto path (optionConfig vals args);
+                  result = recurseInto path (opt.options ++ imap (index: v: args: {
+                    key = rec {
+                      #!!! Would be nice if we had the file the val was from
+                      option = path;
+                      number = index;
+                      outPath = "option ${option} config number ${toString number}";
+                    };
+                  } // (lib.applyIfFunction v args)) (toList vals)) args;
                   name = lib.removePrefix (opt.name + ".") path;
                   extraArgs = opt.extraArgs or {};
                   individualExtraArgs = opt.individualExtraArgs or {};