diff --git a/docs/docgen.nix b/docs/docgen.nix
index 9838327..c502528 100644
--- a/docs/docgen.nix
+++ b/docs/docgen.nix
@@ -18,33 +18,23 @@ stdenvNoCC.mkDerivation {
   ];
   patchPhase =
     let
-      shouldExclude = relPath: lib.any (pattern: builtins.match pattern relPath != null) excluded;
-
+      relPath = file: lib.removePrefix (toString ../. + "/") (toString file);
       nixFiles =
         with lib.fileset;
-        let
-          allFiles = toList (fileFilter (f: f.hasExt "nix") ../.);
-        in
-        lib.filter (
-          file:
-          let
-            relPath = lib.removePrefix (toString ../. + "/") (toString file);
-          in
-          !shouldExclude relPath
-        ) allFiles;
+        lib.filter (file: !(lib.any (pattern: builtins.match pattern (relPath file) != null) excluded)) (
+          toList (fileFilter (f: f.hasExt "nix") ../.)
+        );
 
       chapters = lib.sort (a: b: a.sortKey < b.sortKey) (
         map (
           file:
           let
-
-            relPath = lib.removePrefix (toString ../. + "/") (toString file);
             mdPath =
               (
                 if baseNameOf file == "default.nix" then
-                  lib.removeSuffix "/" (dirOf relPath)
+                  lib.removeSuffix "/" (dirOf (relPath file))
                 else
-                  lib.removeSuffix ".nix" relPath
+                  lib.removeSuffix ".nix" (relPath file)
               )
               + ".md";
 
@@ -55,7 +45,7 @@ stdenvNoCC.mkDerivation {
               hosts = 3;
               users = 4;
             };
-            order = orderMap.${lib.head (lib.splitString "/" relPath)};
+            order = orderMap.${lib.head (lib.splitString "/" (relPath file))};
 
             category = lib.removeSuffix ".md" (lib.replaceStrings [ "/" ] [ "." ] mdPath);
             title =