diff --git a/nixos/doc/manual/development/settings-options.section.md b/nixos/doc/manual/development/settings-options.section.md
index 48cc62bb424c..b37cd1d34525 100644
--- a/nixos/doc/manual/development/settings-options.section.md
+++ b/nixos/doc/manual/development/settings-options.section.md
@@ -312,6 +312,8 @@ have a predefined type and string generator already declared under
     may be transformed into multiple key-value pairs depending on
     `listToValue`).
 
+    The attribute `lib.type.atom` contains the used INI atom.
+
 `pkgs.formats.iniWithGlobalSection` { *`listsAsDuplicateKeys`* ? false, *`listToValue`* ? null, \.\.\. }
 
 :   A function taking an attribute set with values
@@ -333,6 +335,8 @@ have a predefined type and string generator already declared under
     attrset of key-value pairs for a single section, the global section which
     preceedes the section definitions.
 
+    The attribute `lib.type.atom` contains the used INI atom.
+
 `pkgs.formats.toml` { }
 
 :   A function taking an empty attribute set (for future extensibility)
diff --git a/nixos/modules/services/mail/public-inbox.nix b/nixos/modules/services/mail/public-inbox.nix
index 98063e0331bd..1f7c8c44ace1 100644
--- a/nixos/modules/services/mail/public-inbox.nix
+++ b/nixos/modules/services/mail/public-inbox.nix
@@ -7,7 +7,7 @@ let
   stateDir = "/var/lib/public-inbox";
 
   gitIni = pkgs.formats.gitIni { listsAsDuplicateKeys = true; };
-  iniAtom = elemAt gitIni.type/*attrsOf*/.functor.wrapped/*attrsOf*/.functor.wrapped/*either*/.functor.wrapped 0;
+  iniAtom = gitIni.lib.types.atom;
 
   useSpamAssassin = cfg.settings.publicinboxmda.spamcheck == "spamc" ||
                     cfg.settings.publicinboxwatch.spamcheck == "spamc";
diff --git a/pkgs/pkgs-lib/formats.nix b/pkgs/pkgs-lib/formats.nix
index 03663ad96b97..1a8df5ff380b 100644
--- a/pkgs/pkgs-lib/formats.nix
+++ b/pkgs/pkgs-lib/formats.nix
@@ -123,9 +123,9 @@ rec {
           }
         else
           singleIniAtom;
-      iniSection = { listsAsDuplicateKeys, listToValue, atomsCoercedToLists }@args:
-        attrsOf (iniAtom args) // {
-          description = "section of an INI file (attrs of " + (iniAtom args).description + ")";
+      iniSection = atom:
+        attrsOf atom // {
+          description = "section of an INI file (attrs of " + atom.description + ")";
         };
 
       maybeToList = listToValue: if listToValue != null then lib.mapAttrs (key: val: if lib.isList val then listToValue val else val) else lib.id;
@@ -144,12 +144,14 @@ rec {
         assert atomsCoercedToLists != null -> (listsAsDuplicateKeys || listToValue != null);
         let
           atomsCoercedToLists' = if atomsCoercedToLists == null then false else atomsCoercedToLists;
+          atom = iniAtom { inherit listsAsDuplicateKeys listToValue; atomsCoercedToLists = atomsCoercedToLists'; };
         in
         {
 
         type = lib.types.attrsOf (
-          iniSection { inherit listsAsDuplicateKeys listToValue; atomsCoercedToLists = atomsCoercedToLists'; }
+          iniSection atom
         );
+        lib.types.atom = atom;
 
         generate = name: value:
           lib.pipe value
@@ -174,24 +176,26 @@ rec {
         assert atomsCoercedToLists != null -> (listsAsDuplicateKeys || listToValue != null);
         let
           atomsCoercedToLists' = if atomsCoercedToLists == null then false else atomsCoercedToLists;
+          atom = iniAtom { inherit listsAsDuplicateKeys listToValue; atomsCoercedToLists = atomsCoercedToLists'; };
         in
         {
           type = lib.types.submodule {
             options = {
               sections = lib.mkOption rec {
                 type = lib.types.attrsOf (
-                  iniSection { inherit listsAsDuplicateKeys listToValue; atomsCoercedToLists = atomsCoercedToLists'; }
+                  iniSection atom
                 );
                 default = {};
                 description = type.description;
               };
               globalSection = lib.mkOption rec {
-                type = iniSection { inherit listsAsDuplicateKeys listToValue; atomsCoercedToLists = atomsCoercedToLists'; };
+                type = iniSection atom;
                 default = {};
                 description = "global " + type.description;
               };
             };
           };
+          lib.types.atom = atom;
           generate = name: { sections ? {}, globalSection ? {}, ... }:
             pkgs.writeText name (lib.generators.toINIWithGlobalSection (removeAttrs args ["listToValue" "atomsCoercedToLists"])
             {
@@ -200,17 +204,19 @@ rec {
             });
         };
 
-      gitIni = { listsAsDuplicateKeys ? false, ... }@args: {
-        type = let
+      gitIni = { listsAsDuplicateKeys ? false, ... }@args:
+        let
           atom = iniAtom {
-            listsAsDuplicateKeys = listsAsDuplicateKeys;
+            inherit listsAsDuplicateKeys;
             listToValue = null;
             atomsCoercedToLists = false;
           };
-        in attrsOf (attrsOf (either atom (attrsOf atom)));
-
-        generate = name: value: pkgs.writeText name (lib.generators.toGitINI value);
-      };
+        in
+        {
+          type = attrsOf (attrsOf (either atom (attrsOf atom)));
+          lib.types.atom = atom;
+          generate = name: value: pkgs.writeText name (lib.generators.toGitINI value);
+        };
 
     }) ini iniWithGlobalSection gitIni;