diff --git a/cabal2nix/hackage2nix/Main.hs b/cabal2nix/hackage2nix/Main.hs
index 370f3324..85223bb3 100644
--- a/cabal2nix/hackage2nix/Main.hs
+++ b/cabal2nix/hackage2nix/Main.hs
@@ -78,8 +78,13 @@ main = do
               )
   CLI {..} <- execParser pinfo
 
+  let nixpkgsArgs = mconcat [ "{"
+                            , "overlays = [ (self: super: { haskellPackages = self.lib.dontRecurseIntoAttrs super.haskellPackages; }) ];"
+                            , "config.allowAliases = false;"
+                            , "}"
+                            ]
   config <- sconcat <$> mapM (\file -> readConfiguration (nixpkgsRepository </> file)) configFiles
-  nixpkgs <- readNixpkgPackageMap nixpkgsRepository (Just "{ config = { allowAliases = false; }; }")
+  nixpkgs <- readNixpkgPackageMap nixpkgsRepository (Just nixpkgsArgs)
   preferredVersions <- readPreferredVersions (fromMaybe (hackageRepository </> "preferred-versions") preferredVersionsFile)
   let fixup = Map.delete "acme-everything"      -- TODO: https://github.com/NixOS/cabal2nix/issues/164
             . Map.delete "type"                 -- TODO: https://github.com/NixOS/cabal2nix/issues/163
diff --git a/shell.nix b/shell.nix
index 25837083..df50466f 100644
--- a/shell.nix
+++ b/shell.nix
@@ -1,8 +1,8 @@
 { pkgs ?
     import (builtins.fetchTarball {
-      # nixos-unstable 2025-04-23
-      url = "https://github.com/nixos/nixpkgs/archive/96d30055a2215e5c5a545872376137a5d063e804.tar.gz";
-      sha256 = "0xvzkpgc8qy4q252c3x399c8ikrks970c877s4i7vppnhxp08p8n";
+      # nixos-unstable 2025-08-10
+      url = "https://github.com/nixos/nixpkgs/archive/c9b6fb798541223bbb396d287d16f43520250518.tar.gz";
+      sha256 = "sha256-vgPm2xjOmKdZ0xKA6yLXPJpjOtQPHfaZDRtH+47XEBo=";
     }) { }
 , ghcVersion ? pkgs.haskellPackages.ghc.version
   # Pass --arg minimal true to disable tools that are not strictly necessary