diff --git a/build.nix b/build.nix
index 8bc51e6450..3e232af838 100644
--- a/build.nix
+++ b/build.nix
@@ -5,7 +5,7 @@
 let
   haskellNix = (import ./default.nix {});
 in
-{ nixpkgs ? haskellNix.sources.nixpkgs
+{ nixpkgs ? haskellNix.sources.nixpkgs-2009
 , nixpkgsArgs ? haskellNix.nixpkgsArgs
 , pkgs ? import nixpkgs nixpkgsArgs
 , ifdLevel ? 1000
diff --git a/ci.nix b/ci.nix
index 4c004c5086..2912e36771 100644
--- a/ci.nix
+++ b/ci.nix
@@ -10,6 +10,7 @@
   sources = import ./nix/sources.nix {};
   nixpkgsVersions = {
     "R2009" = "nixpkgs-2009";
+    "R2105" = "nixpkgs-2105";
     "unstable" = "nixpkgs-unstable";
   };
   compilerNixNames = nixpkgsName: nixpkgs: builtins.mapAttrs (compiler-nix-name: runTests: {
@@ -22,10 +23,10 @@
     # cabal-install and nix-tools plans.  When removing a ghc version
     # from here (so that is no longer cached) also remove ./materialized/ghcXXX.
     # Update supported-ghc-versions.md to reflect any changes made here.
-    {
+    nixpkgs.lib.optionalAttrs (nixpkgsName == "R2009") {
       ghc865 = false;
-      ghc8105 = false; # Just included because the native version is needed at eval time
-    } // nixpkgs.lib.optionalAttrs (nixpkgsName == "R2009") {
+      ghc8105 = false;
+    } // nixpkgs.lib.optionalAttrs (nixpkgsName == "R2105") {
       ghc865 = false;
       ghc8105 = true;
     } // nixpkgs.lib.optionalAttrs (nixpkgsName == "unstable") {
diff --git a/nix/sources.json b/nix/sources.json
index 7cdcbb336f..8f1ddecaa2 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -91,16 +91,16 @@
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs": {
-        "branch": "nixpkgs-20.09-darwin",
+        "branch": "nixpkgs-21.05-darwin",
         "builtin": false,
         "description": "Nix Packages collection",
         "homepage": null,
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "f02bf8ffb9a5ec5e8f6f66f1e5544fd2aa1a0693",
-        "sha256": "156f48manydh8sbrs8j97mzvwdz2zaw51xlm0grrrnns5wa5aaln",
+        "rev": "3c6f3f84af60a8ed5b8a79cf3026b7630fcdefb8",
+        "sha256": "0jf9l6j60sa8cms7r4a02kr9j9884pwv1prf79b2ysnxmnhimnch",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/f02bf8ffb9a5ec5e8f6f66f1e5544fd2aa1a0693.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/3c6f3f84af60a8ed5b8a79cf3026b7630fcdefb8.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs-2003": {
@@ -110,10 +110,10 @@
         "homepage": null,
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "7f73e46625f508a793700f5110b86f1a53341d6e",
-        "sha256": "1gijn6vm6hwy7sxdjd27qq0hjqpkq04npwbxybd9694x7h806823",
+        "rev": "1db42b7fe3878f3f5f7a4f2dc210772fd080e205",
+        "sha256": "05k9y9ki6jhaqdhycnidnk5zrdzsdammbk5lsmsbz249hjhhgcgh",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/7f73e46625f508a793700f5110b86f1a53341d6e.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/1db42b7fe3878f3f5f7a4f2dc210772fd080e205.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs-2009": {
@@ -123,10 +123,23 @@
         "homepage": null,
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "f02bf8ffb9a5ec5e8f6f66f1e5544fd2aa1a0693",
-        "sha256": "156f48manydh8sbrs8j97mzvwdz2zaw51xlm0grrrnns5wa5aaln",
+        "rev": "46d1c3f28ca991601a53e9a14fdd53fcd3dd8416",
+        "sha256": "1h7lfhqws2cf8zg30fj8pakh4aw0id3m9yjpgn21scdv2nwkyyxa",
+        "type": "tarball",
+        "url": "https://github.com/NixOS/nixpkgs/archive/46d1c3f28ca991601a53e9a14fdd53fcd3dd8416.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
+    },
+    "nixpkgs-2105": {
+        "branch": "nixpkgs-21.05-darwin",
+        "builtin": false,
+        "description": "Nix Packages collection",
+        "homepage": null,
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "3c6f3f84af60a8ed5b8a79cf3026b7630fcdefb8",
+        "sha256": "0jf9l6j60sa8cms7r4a02kr9j9884pwv1prf79b2ysnxmnhimnch",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/f02bf8ffb9a5ec5e8f6f66f1e5544fd2aa1a0693.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/3c6f3f84af60a8ed5b8a79cf3026b7630fcdefb8.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs-unstable": {
@@ -136,10 +149,10 @@
         "homepage": "",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "d8eb97e3801bde96491535f40483d550b57605b9",
-        "sha256": "1bdd7jinq5d40qai45jfkbcw1n96c7fdlams5iidwzy2ag8axlqh",
+        "rev": "0747387223edf1aa5beaedf48983471315d95e16",
+        "sha256": "19hpz87vfcr6icxcjdlp2mnk8v5db4l3x32adzc5ynmxvfayg3lr",
         "type": "tarball",
-        "url": "https://github.com/NixOS/nixpkgs/archive/d8eb97e3801bde96491535f40483d550b57605b9.tar.gz",
+        "url": "https://github.com/NixOS/nixpkgs/archive/0747387223edf1aa5beaedf48983471315d95e16.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "old-ghc-nix": {
diff --git a/overlays/emscripten.nix b/overlays/emscripten.nix
index ec0c398375..8f03c09229 100644
--- a/overlays/emscripten.nix
+++ b/overlays/emscripten.nix
@@ -2,6 +2,8 @@ final: prev: let
   # GHCJS currently requires an old version of emscripten. Overriding to build the older version doesn't
   # work straightforwardly on 20.09 anymore, so we use an ugly hack and pull emscripten from 20.03.
   # In future, we'll just fix GHCJS to work with the newer emscripten.
+
+  # Not sure what to do here - akrmn
   pkgs-2003 = import final.haskell-nix.sources.nixpkgs-2003 {
     system = final.stdenv.system;
     overlays = [(final: prev: with final; {
diff --git a/release.nix b/release.nix
index 6514968ada..3ccf087c2a 100644
--- a/release.nix
+++ b/release.nix
@@ -15,8 +15,8 @@ let
     # added here will also included without aggregation, making it easier
     # to find a failing test.  Keep in mind though that adding too many
     # of these will slow down eval times.
-    linux = allJobs.R2009.ghc8105.linux.native or {};
-    darwin = allJobs.R2009.ghc8105.darwin.native or {};
+    linux = allJobs.R2105.ghc8105.linux.native or {};
+    darwin = allJobs.R2105.ghc8105.darwin.native or {};
   };
   names = x: lib.filter (n: n != "recurseForDerivations" && n != "meta")
     (builtins.attrNames x);