diff --git a/checks.nix b/checks.nix
index f59691d..73bb423 100644
--- a/checks.nix
+++ b/checks.nix
@@ -37,7 +37,7 @@ let
   };
   mkDoom = args: (makeDoomPackages (common // args)).doomEmacs;
   mkDoomDir = args: writeTextDir "init.el" (toInit args);
-  minimalDoomDir = mkDoomDir { config = [ "default" ]; };
+  minimalDoomDir = mkDoomDir { config.default = true; };
   doomTest = name: init: doomArgs: testers.testEqualContents {
     assertion = "name = ${name}; modules = ${toPretty {} init}; args = ${toPretty {} doomArgs};";
     expected = writeText "doom-expected" "Doom functions";
@@ -77,14 +77,14 @@ in {
     doomDir = ./doomdir;
     profileName = "";
   };
-  interactive = doomTest "nix-profile" { config = [ "default" ]; } { };
-  interactive-without-loader = doomTest "no-profile" { config = [ "default" ]; } { profileName = ""; };
-  interactive-no-profile-hack = doomTest "no-profile" { config = [ "default" ]; } { noProfileHack = true; };
+  interactive = doomTest "nix-profile" { config.default = true; } { };
+  interactive-without-loader = doomTest "no-profile" { config.default = true; } { profileName = ""; };
+  interactive-no-profile-hack = doomTest "no-profile" { config.default = true; } { noProfileHack = true; };
 
-  org-re-reveal = doomTest "org-re-reveal" { lang = [ [ "org" "+present" ] ]; } { };
+  org-re-reveal = doomTest "org-re-reveal" { lang.org = [ "+present" ]; } { };
 
   # Various tests of module combinations.
-  unpinned-org = doomTest "external-org" { app = [ [ "rss" "+org" ] ]; } { };
+  unpinned-org = doomTest "external-org" { app.rss = [ "+org" ]; } { };
 
-  extraPackages = doomTest "extraPackages" { config = [ "default" ]; } { extraPackages = epkgs: [ epkgs.vterm ]; };
+  extraPackages = doomTest "extraPackages" { config.default = true; } { extraPackages = epkgs: [ epkgs.vterm ]; };
 }
diff --git a/flake.nix b/flake.nix
index 39250e7..94c2a8d 100644
--- a/flake.nix
+++ b/flake.nix
@@ -52,8 +52,14 @@
     in
       pkgs.callPackages self mergedArgs;
 
+    # Convert a Nix expression to a `doom!` block suitable for init.el.
+    #
+    # Input: a nested attribute set.
+    # The keys of the first level are categories (like `lang`).
+    # The keys of the second level are module names (like `nix`).
+    # The values are lists of module flags, or `true` for no flags.
     toInit = let
-      inherit (nixpkgs.lib) concatLines concatStringsSep isList isString mapAttrsToList toPretty;
+      inherit (nixpkgs.lib) concatLines concatStringsSep isList mapAttrsToList toPretty;
     in
       attrs:
       concatLines (
@@ -62,11 +68,11 @@
           cat: modules:
           (concatLines (
             [ (":" + cat) ]
-            ++ (map (
-              mod:
-              if isString mod then mod
-              else if isList mod then "(" + (concatStringsSep " " mod) + ")"
-              else abort "${toPretty mod} not supported"
+            ++ (mapAttrsToList (
+              mod: value:
+              if value == true then mod
+              else if isList value then "(${mod} ${concatStringsSep " " value})"
+              else abort "${toPretty value} not supported"
             ))
               modules
           ))