diff --git a/default.nix b/default.nix
index 59272d9..7b5f2a1 100644
--- a/default.nix
+++ b/default.nix
@@ -13,5 +13,5 @@ in
   compiler-nix-name = "ghc928";
 
   # Specify the hackage index state
-  index-state = "2023-07-20T00:00:00Z";
+  index-state = "2023-11-24T00:00:00Z";
 }
diff --git a/h8x.nix b/h8x.nix
index e9c5e2a..70d571d 100644
--- a/h8x.nix
+++ b/h8x.nix
@@ -1,6 +1,7 @@
 let
-  # Pin haskell-nix to a recent (as of 2023/07/20) commit
-  h8x-pin = "https://github.com/input-output-hk/haskell.nix/archive/3ae883bb7864ba85c3aab30f8f488b9a7d84afc8.tar.gz";
+  # Pin haskell-nix to a recent (as of 2023/11/24) commit
+  h8x-commit = "c6e3c91844e91f86cb64015258eed2ed8545d2a9";
+  h8x-pin = "https://github.com/input-output-hk/haskell.nix/archive/${h8x-commit}.tar.gz";
   h8x-src = builtins.fetchTarball h8x-pin;
   h8x = import h8x-src {};
 
@@ -11,7 +12,7 @@ in
     # hence you will be more likely to get cache hits when using these. But you
     # can also just use your own, e.g. '<nixpkgs>'.
 
-    h8x.sources.nixpkgs-2305
+    h8x.sources.nixpkgs-unstable
 
     # These arguments passed to nixpkgs, include some patches and also the
     # haskell.nix functionality itself as an overlay.
diff --git a/shell.nix b/shell.nix
index c3c388f..7dcdc1e 100644
--- a/shell.nix
+++ b/shell.nix
@@ -12,7 +12,7 @@ in
       hlint = "latest"; # Selects the latest version in the hackage.nix snapshot
       haskell-language-server = "latest";
       ghcid = "latest";
-      fourmolu = "latest";
+      fourmolu = "0.14.0.0";
       cabal-fmt = "latest";
     };
     # See overlays/tools.nix for more details