diff --git a/nixos/modules/installer/tools/nixos-option.sh b/nixos/modules/installer/tools/nixos-option.sh
index a2b963d7661..b5f69f07826 100644
--- a/nixos/modules/installer/tools/nixos-option.sh
+++ b/nixos/modules/installer/tools/nixos-option.sh
@@ -76,14 +76,23 @@ evalAttr(){
   local prefix="$1"
   local strict="$2"
   local suffix="$3"
+
+  # If strict is set, then set it to "true".
+  test -n "$strict" && strict=true
+
   evalNix ${strict:+--strict} <<EOF
 let
   reach = attrs: attrs${option:+.$option}${suffix:+.$suffix};
   nixos = import <nixos> {};
   nixpkgs = import <nixpkgs> {};
+  strict = ${strict:-false};
   cleanOutput = x: with nixpkgs.lib;
     if isDerivation x then x.outPath
     else if isFunction x then "<CODE>"
+    else if strict then
+      if isAttrs x then mapAttrs (n: cleanOutput) x
+      else if isList x then map cleanOutput x
+      else x
     else x;
 in
   cleanOutput (reach nixos.$prefix)