1 files changed, 18 insertions, 7 deletions
diff --git a/nixpkgs/lib/modules.nix b/nixpkgs/lib/modules.nix
index b124ea000a2e..46ae3f136310 100644
--- a/nixpkgs/lib/modules.nix
+++ b/nixpkgs/lib/modules.nix
@@ -162,13 +162,24 @@ rec {
             baseMsg = "The option `${showOption (prefix ++ firstDef.prefix)}' does not exist. Definition values:${showDefs [ firstDef ]}";
           in
             if attrNames options == [ "_module" ]
-              then throw ''
-                ${baseMsg}
-
-                However there are no options defined in `${showOption prefix}'. Are you sure you've
-                declared your options properly? This can happen if you e.g. declared your options in `types.submodule'
-                under `config' rather than `options'.
-              ''
+              then
+                let
+                  optionName = showOption prefix;
+                in
+                  if optionName == ""
+                    then throw ''
+                      ${baseMsg}
+
+                      It seems as if you're trying to declare an option by placing it into `config' rather than `options'!
+                    ''
+                  else
+                    throw ''
+                      ${baseMsg}
+
+                      However there are no options defined in `${showOption prefix}'. Are you sure you've
+                      declared your options properly? This can happen if you e.g. declared your options in `types.submodule'
+                      under `config' rather than `options'.
+                    ''
             else throw baseMsg
         else null;