diff --git a/pkgs/development/haskell-modules/cabal2nix-unstable/cabal2nix.nix b/pkgs/development/haskell-modules/cabal2nix-unstable/cabal2nix.nix
index dc82033beeef..79a33626af3f 100644
--- a/pkgs/development/haskell-modules/cabal2nix-unstable/cabal2nix.nix
+++ b/pkgs/development/haskell-modules/cabal2nix-unstable/cabal2nix.nix
@@ -35,10 +35,10 @@
 }:
 mkDerivation {
   pname = "cabal2nix";
-  version = "2.20.1-unstable-2025-11-11";
+  version = "2.20.1-unstable-2025-11-20";
   src = fetchzip {
-    url = "https://github.com/NixOS/cabal2nix/archive/a152152295a9fa6698583e84a2b8c7eee1446296.tar.gz";
-    sha256 = "1jpgzyc360g5snvc5ji6wqfvbsc7siwxvhrwafzzfg762niq0c49";
+    url = "https://github.com/NixOS/cabal2nix/archive/be62a6c198c6fd082cd5660170fa23a709d92c8e.tar.gz";
+    sha256 = "15bfhl0ypnnpgglxc7smppqi3w8w04zi97gh65kk1p6drlg29f47";
   };
   postUnpack = "sourceRoot+=/cabal2nix; echo source root reset to $sourceRoot";
   isLibrary = true;
diff --git a/pkgs/development/haskell-modules/cabal2nix-unstable/distribution-nixpkgs.nix b/pkgs/development/haskell-modules/cabal2nix-unstable/distribution-nixpkgs.nix
index 00afd0bb28c4..aab109281ebf 100644
--- a/pkgs/development/haskell-modules/cabal2nix-unstable/distribution-nixpkgs.nix
+++ b/pkgs/development/haskell-modules/cabal2nix-unstable/distribution-nixpkgs.nix
@@ -18,10 +18,10 @@
 }:
 mkDerivation {
   pname = "distribution-nixpkgs";
-  version = "1.7.1.1-unstable-2025-11-11";
+  version = "1.7.1.1-unstable-2025-11-20";
   src = fetchzip {
-    url = "https://github.com/NixOS/cabal2nix/archive/a152152295a9fa6698583e84a2b8c7eee1446296.tar.gz";
-    sha256 = "1jpgzyc360g5snvc5ji6wqfvbsc7siwxvhrwafzzfg762niq0c49";
+    url = "https://github.com/NixOS/cabal2nix/archive/be62a6c198c6fd082cd5660170fa23a709d92c8e.tar.gz";
+    sha256 = "15bfhl0ypnnpgglxc7smppqi3w8w04zi97gh65kk1p6drlg29f47";
   };
   postUnpack = "sourceRoot+=/distribution-nixpkgs; echo source root reset to $sourceRoot";
   enableSeparateDataOutput = true;
diff --git a/pkgs/development/haskell-modules/cabal2nix-unstable/hackage-db.nix b/pkgs/development/haskell-modules/cabal2nix-unstable/hackage-db.nix
index 2ad97d7259df..f99b95e475c4 100644
--- a/pkgs/development/haskell-modules/cabal2nix-unstable/hackage-db.nix
+++ b/pkgs/development/haskell-modules/cabal2nix-unstable/hackage-db.nix
@@ -17,10 +17,10 @@
 }:
 mkDerivation {
   pname = "hackage-db";
-  version = "2.1.3-unstable-2025-11-11";
+  version = "2.1.3-unstable-2025-11-20";
   src = fetchzip {
-    url = "https://github.com/NixOS/cabal2nix/archive/a152152295a9fa6698583e84a2b8c7eee1446296.tar.gz";
-    sha256 = "1jpgzyc360g5snvc5ji6wqfvbsc7siwxvhrwafzzfg762niq0c49";
+    url = "https://github.com/NixOS/cabal2nix/archive/be62a6c198c6fd082cd5660170fa23a709d92c8e.tar.gz";
+    sha256 = "15bfhl0ypnnpgglxc7smppqi3w8w04zi97gh65kk1p6drlg29f47";
   };
   postUnpack = "sourceRoot+=/hackage-db; echo source root reset to $sourceRoot";
   isLibrary = true;
diff --git a/pkgs/development/haskell-modules/cabal2nix-unstable/language-nix.nix b/pkgs/development/haskell-modules/cabal2nix-unstable/language-nix.nix
index d0e04dc856ab..2c863d4df1b7 100644
--- a/pkgs/development/haskell-modules/cabal2nix-unstable/language-nix.nix
+++ b/pkgs/development/haskell-modules/cabal2nix-unstable/language-nix.nix
@@ -9,14 +9,15 @@
   lib,
   parsec-class,
   pretty,
+  process,
   QuickCheck,
 }:
 mkDerivation {
   pname = "language-nix";
-  version = "2.3.0-unstable-2025-11-11";
+  version = "2.3.0-unstable-2025-11-20";
   src = fetchzip {
-    url = "https://github.com/NixOS/cabal2nix/archive/a152152295a9fa6698583e84a2b8c7eee1446296.tar.gz";
-    sha256 = "1jpgzyc360g5snvc5ji6wqfvbsc7siwxvhrwafzzfg762niq0c49";
+    url = "https://github.com/NixOS/cabal2nix/archive/be62a6c198c6fd082cd5660170fa23a709d92c8e.tar.gz";
+    sha256 = "15bfhl0ypnnpgglxc7smppqi3w8w04zi97gh65kk1p6drlg29f47";
   };
   postUnpack = "sourceRoot+=/language-nix; echo source root reset to $sourceRoot";
   libraryHaskellDepends = [
@@ -33,6 +34,7 @@ mkDerivation {
     lens
     parsec-class
     pretty
+    process
     QuickCheck
   ];
   homepage = "https://github.com/NixOS/cabal2nix/tree/master/language-nix#readme";
diff --git a/pkgs/development/haskell-modules/configuration-nix.nix b/pkgs/development/haskell-modules/configuration-nix.nix
index 526a96d59fc3..b9fde329d049 100644
--- a/pkgs/development/haskell-modules/configuration-nix.nix
+++ b/pkgs/development/haskell-modules/configuration-nix.nix
@@ -1531,6 +1531,18 @@ builtins.intersectAttrs super {
     };
   }) (enableSeparateBinOutput super.cabal2nix-unstable);
 
+  # Cabal doesn't allow us to properly specify the test dependency
+  # on nix-instantiate(1). Even though we're just evaluating pure code,
+  # it absolutely wants to write to disk.
+  language-nix-unstable = overrideCabal (drv: {
+    testDepends = drv.testDepends or [ ] ++ [ pkgs.nix ];
+    preCheck = ''
+      export TMP_NIX_DIR="$(mktemp -d)"
+      export NIX_STORE_DIR="$TMP_NIX_DIR/store"
+      export NIX_STATE_DIR="$TMP_NIX_DIR/state"
+    '';
+  }) super.language-nix-unstable;
+
   # test suite needs local redis daemon
   nri-redis = dontCheck super.nri-redis;