diff --git a/home-manager/roles/neovim/default.nix b/home-manager/roles/neovim/default.nix
index 20fd3375..853fdcbb 100644
--- a/home-manager/roles/neovim/default.nix
+++ b/home-manager/roles/neovim/default.nix
@@ -88,7 +88,7 @@ let
 in {
   home = {
     file.".config/nvim/coc-settings.json".text = builtins.toJSON cocSettings;
-    packages = [ neovim pkgs.neuron-language-server];
+    packages = [ neovim pkgs.neuron-language-server ];
     sessionVariables.EDITOR = "${neovim}/bin/nvim";
   };
 }
diff --git a/nix/sources.json b/nix/sources.json
index f3948985..88d9709c 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -53,10 +53,10 @@
         "homepage": null,
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "51d115ac89d676345b05a0694b23bd2691bf708a",
-        "sha256": "1gfjaa25nq4vprs13h30wasjxh79i67jj28v54lkj4ilqjhgh2rs",
+        "rev": "4bd1938e03e1caa49a6da1ec8cff802348458f05",
+        "sha256": "0529npmibafjr80i2bhqg22pjr3d5qz1swjcq2jkdla1njagkq2k",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/51d115ac89d676345b05a0694b23bd2691bf708a.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/4bd1938e03e1caa49a6da1ec8cff802348458f05.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs-master": {
@@ -71,6 +71,18 @@
         "url": "https://github.com/NixOS/nixpkgs/archive/75dd59019ca3043d29ec6fbb3f69d9bcb46d2113.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
+    "nixpkgs-release": {
+        "branch": "release-20.03",
+        "description": "Nixpkgs/NixOS branches that track the Nixpkgs/NixOS channels",
+        "homepage": null,
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "0da54872f9da4649099118b8f59e85a4256cc45c",
+        "sha256": "17f63bz3l6j8iyxifmk12qvn0rkxi53yrv294q8sghcqrw0qhr98",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs/archive/0da54872f9da4649099118b8f59e85a4256cc45c.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
     "obelisk": {
         "branch": "master",
         "description": "Obelisk provides an easy way to develop and deploy your Reflex project for web and mobile",
diff --git a/overlays/10-previews.nix b/overlays/10-previews.nix
index 08fbccc7..a7559872 100644
--- a/overlays/10-previews.nix
+++ b/overlays/10-previews.nix
@@ -8,6 +8,6 @@ in {
     inherit (unstable.gnome3) gnome-keyring seahorse gdm;
   };
   inherit (unstable)
-    aqbanking neovim vimPlugins syncthing nerdfonts ormolu ghcid go-neb;
+    aqbanking neovim vimPlugins syncthing nerdfonts ormolu ghcid go-neb fzf nixpkgs-fmt;
   inherit (nixpkgs-master) element-web element-desktop;
 }
diff --git a/overlays/20-unfree.nix b/overlays/20-unfree.nix
index 3db9e1c8..094e5399 100644
--- a/overlays/20-unfree.nix
+++ b/overlays/20-unfree.nix
@@ -4,4 +4,5 @@ if super.config.allowUnfree or false then
 else {
   unfree = import self.sources.nixpkgs { config.allowUnfree = true; };
   unstableUnfree = import self.sources.unstable { config.allowUnfree = true; };
+  releaseUnfree = import self.sources.nixpkgs-release { config.allowUnfree = true; };
 }
diff --git a/overlays/30-ghc.nix b/overlays/30-ghc.nix
index 6ec621a2..833dbca6 100644
--- a/overlays/30-ghc.nix
+++ b/overlays/30-ghc.nix
@@ -1,10 +1,11 @@
 self: super:
 let
+  inherit (super) fetchFromGitHub;
   master = import super.sources.nixpkgs-master { };
   inherit (master.haskell.lib) overrideCabal unmarkBroken;
   myOverrides = self: super: {
     optics = super.optics_0_3;
-    optics-th = super.optics-th_0_3_0_1;
+    optics-th = super.optics-th_0_3_0_2;
     optics-core = super.optics-core_0_3_0_1;
     optics-extra = super.optics-extra_0_3;
   };
@@ -24,5 +25,5 @@ in {
   myHaskellPackages = makeHaskellPackages master.haskellPackages;
   scriptGhc = master.ghc.withPackages
     (p: builtins.attrValues (makeHaskellScriptPackages p));
-  ghc = master.ghc.withHoogle (p: builtins.attrValues (makeHaskellPackages p));
+  ghc = (master.haskellPackages.override { overrides = myOverrides; }).ghc.withHoogle (p: builtins.attrValues (makeHaskellPackages p));
 }
diff --git a/overlays/neuron-language-server/package.nix b/overlays/neuron-language-server/package.nix
index a35a04f3..0b938c51 100644
--- a/overlays/neuron-language-server/package.nix
+++ b/overlays/neuron-language-server/package.nix
@@ -7,7 +7,7 @@ buildGoModule {
     owner = "aca";
     repo = "neuron-language-server";
     rev = "master";
-    sha256 = "02vj5szqric7zbm8fbw9ngg4dwrgi3nss6a4kv28bqjr1zm3zn4v";
+    sha256 = "1kbh0bzzfmk7aj3c6k3ifwx4p42lw2pnr68srk3qpy6hjna8nczb";
   };
 
   vendorSha256 = "02dajl4l3c8522ik2hmiq8cx4kj4h2ykx8l7qsal5xznx9pqbs7i";
diff --git a/overlays/pkgSets.nix b/overlays/pkgSets.nix
index c1581428..26ea9dc7 100644
--- a/overlays/pkgSets.nix
+++ b/overlays/pkgSets.nix
@@ -45,7 +45,7 @@ self: super: {
     inherit (self.pythonPackages) yapf jsbeautifier;
     inherit (self)
       go gdb mpc_cli ncmpcpp shfmt htmlTidy astyle nodejs tasksh magic-wormhole
-      nixfmt rnix-lsp tmate rustup kitty nix-top ghc ghcid;
+      nixfmt nixpkgs-fmt rnix-lsp tmate rustup kitty nix-top ghc ghcid;
     obelisk = (import self.sources.obelisk { }).command;
   };
   accounting-pkgs = {