diff --git a/default.nix b/default.nix
index 8e43241a..902fcc94 100644
--- a/default.nix
+++ b/default.nix
@@ -378,9 +378,30 @@ let
 in
 
 {
-  inherit superbol-studio-oss superbol-free superbol_free_lib vscode-json ppx_cobcflags cobol_lsp
-            superbol_project ezr_toml ez_toml superbol_preprocs sql_parser sql_ast cobol_cfg
-            cobol_typeck cobol_parser cobol_unit cobol_preproc ebcdic_lib cobol_data cobol_ptree
-            cobol_indent cobol_config cobol_common;
+  inherit
+    superbol-studio-oss
+    superbol-free
+    superbol_free_lib
+    vscode-json
+    ppx_cobcflags
+    cobol_lsp
+    superbol_project
+    ezr_toml
+    ez_toml
+    superbol_preprocs
+    sql_parser
+    sql_ast
+    cobol_cfg
+    cobol_typeck
+    cobol_parser
+    cobol_unit
+    cobol_preproc
+    ebcdic_lib
+    cobol_data
+    cobol_ptree
+    cobol_indent
+    cobol_config
+    cobol_common
+    pretty;
 }
 
diff --git a/nix/default.nix b/nix/default.nix
index e437e652..137c9fb5 100644
--- a/nix/default.nix
+++ b/nix/default.nix
@@ -4,7 +4,7 @@ import sources.nixpkgs {
   overlays = [
     (_: pkgs: { inherit sources; })
     (_: pkgs: {
-        ocamlPackages = pkgs.ocaml-ng.ocamlPackages_4_14.overrideScope' (self: super: {
+        ocamlPackages = pkgs.ocaml-ng.ocamlPackages_4_14.overrideScope (self: super: {
           ez_api = pkgs.callPackage ./ez_api.nix { };
           ez_cmdliner = pkgs.callPackage ./ez_cmdliner.nix { };
           ez_file = pkgs.callPackage ./ez_file.nix { };
diff --git a/nix/sources.json b/nix/sources.json
index 4cb32ed8..aa60e7ea 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -63,15 +63,15 @@
         "version": "20231231"
     },
     "nixpkgs": {
-        "branch": "nixos-unstable",
+        "branch": "master",
         "description": "Nix Packages collection",
         "homepage": null,
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "6c43a3495a11e261e5f41e5d7eda2d71dae1b2fe",
-        "sha256": "16f329z831bq7l3wn1dfvbkh95l2gcggdwn6rk3cisdmv2aa3189",
+        "rev": "b4f480fea347cec3ac599d77986aa17a817bb591",
+        "sha256": "1dq2xg36n4yvihdl37rgs89bxi5imd4bl69g7lfpf2x663madyzd",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/6c43a3495a11e261e5f41e5d7eda2d71dae1b2fe.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/b4f480fea347cec3ac599d77986aa17a817bb591.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "ocplib_stuff": {