diff --git a/hosts/hainich/configuration.nix b/hosts/hainich/configuration.nix
index 02ae012..4c7ad8a 100644
--- a/hosts/hainich/configuration.nix
+++ b/hosts/hainich/configuration.nix
@@ -19,7 +19,7 @@
     ./services/monitoring.nix
     ./services/workadventure.nix
     ./services/minecraft.nix
-#   ./services/mattermost.nix
+    ./services/mattermost.nix
   ];
   boot.loader.grub.enable = true;
   boot.loader.grub.version = 2;
diff --git a/nix/sources.json b/nix/sources.json
index 2cf39af..4a36436 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -17,6 +17,26 @@
         "url": "https://github.com/nix-community/home-manager/archive/2aa20ae969f2597c4df10a094440a66e9d7f8c86.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
+    "mattermost-server": {
+        "branch": "release-5.31",
+        "description": "Open source Slack-alternative in Golang and React - Mattermost",
+        "homepage": "https://mattermost.com",
+        "owner": "mattermost",
+        "repo": "mattermost-server",
+        "rev": "7d89f8bc6ef757877572ef12f3c3c018858318d6",
+        "sha256": "18ip32asar8c34zhnf29v3a66a433443pz7rxa2f4vnp0ri1jil6",
+        "type": "tarball",
+        "url": "https://github.com/mattermost/mattermost-server/archive/7d89f8bc6ef757877572ef12f3c3c018858318d6.tar.gz",
+        "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz",
+        "version": "5.34.2"
+    },
+    "mattermost-webapp": {
+        "sha256": "1a1z3p166bs7ygnnbhm8b556wxmljnk2sj4q527jpr437f02fl6z",
+        "type": "tarball",
+        "url": "https://releases.mattermost.com/5.34.2/mattermost-5.34.2-linux-amd64.tar.gz",
+        "url_template": "https://releases.mattermost.com/<version>/mattermost-<version>-linux-amd64.tar.gz",
+        "version": "5.34.2"
+    },
     "mumble-website": {
         "branch": "master",
         "repo": "https://gitlab.infra4future.de/hacc/infra4future/mumble.infra4future.de.git",
diff --git a/pkgs/mattermost/default.nix b/pkgs/mattermost/default.nix
index bde7c2f..5bc26af 100644
--- a/pkgs/mattermost/default.nix
+++ b/pkgs/mattermost/default.nix
@@ -1,18 +1,14 @@
 { stdenv, fetchurl, fetchFromGitHub, buildGoPackage, buildEnv }:
 
 let
-  version = "5.30.3";
+  sources = import ../../nix/sources.nix;
+  version = sources.mattermost-webapp.version;
 
   mattermost-server = buildGoPackage rec {
     pname = "mattermost-server";
     inherit version;
 
-    src = fetchFromGitHub {
-      owner = "mattermost";
-      repo = "mattermost-server";
-      rev = "v${version}";
-      sha256 = "sha256-cqP2gHv3v49EsAp0xVteKeSRSknchclmUV+9d8WN/18=";
-    };
+    src = sources.mattermost-server.outPath;
 
     goPackagePath = "github.com/mattermost/mattermost-server";
 
@@ -27,19 +23,15 @@ let
     pname = "mattermost-webapp";
     inherit version;
 
-    src = fetchurl {
-      url = "https://releases.mattermost.com/${version}/mattermost-${version}-linux-amd64.tar.gz";
-      sha256 = "sha256-ZQKwHZZtyhJEPk05eGZlHSNiQTc/LD+2+4zjfvE278A=";
-    };
+    src = sources.mattermost-webapp;
 
     installPhase = ''
       mkdir -p $out
-      tar --strip 1 --directory $out -xf $src \
-        mattermost/client \
-        mattermost/i18n \
-        mattermost/fonts \
-        mattermost/templates \
-        mattermost/config
+      cp -r client $out
+      cp -r i18n $out
+      cp -r fonts $out
+      cp -r templates $out
+      cp -r config $out
     '';
   };