diff --git a/nixos/modules/services/web-apps/mattermost.nix b/nixos/modules/services/web-apps/mattermost.nix
index 41c52b9653b..853347bf86e 100644
--- a/nixos/modules/services/web-apps/mattermost.nix
+++ b/nixos/modules/services/web-apps/mattermost.nix
@@ -6,14 +6,18 @@ let
 
   cfg = config.services.mattermost;
 
-  defaultConfig = builtins.fromJSON (readFile "${pkgs.mattermost}/config/config.json");
+  defaultConfig = builtins.fromJSON (builtins.replaceStrings [ "\\u0026" ] [ "&" ]
+    (readFile "${pkgs.mattermost}/config/config.json")
+  );
+
+  database = "postgres://${cfg.localDatabaseUser}:${cfg.localDatabasePassword}@localhost:5432/${cfg.localDatabaseName}?sslmode=disable&connect_timeout=10";
 
   mattermostConf = foldl recursiveUpdate defaultConfig
     [ { ServiceSettings.SiteURL = cfg.siteUrl;
         ServiceSettings.ListenAddress = cfg.listenAddress;
         TeamSettings.SiteName = cfg.siteName;
         SqlSettings.DriverName = "postgres";
-        SqlSettings.DataSource = "postgres://${cfg.localDatabaseUser}:${cfg.localDatabasePassword}@localhost:5432/${cfg.localDatabaseName}?sslmode=disable&connect_timeout=10";
+        SqlSettings.DataSource = database;
       }
       cfg.extraConfig
     ];
@@ -175,7 +179,9 @@ in
           mkdir -p ${cfg.statePath}/{data,config,logs}
           ln -sf ${pkgs.mattermost}/{bin,fonts,i18n,templates,client} ${cfg.statePath}
         '' + lib.optionalString (!cfg.mutableConfig) ''
-          ln -sf ${mattermostConfJSON} ${cfg.statePath}/config/config.json
+          rm -f ${cfg.statePath}/config/config.json
+          cp ${mattermostConfJSON} ${cfg.statePath}/config/config.json
+          ${pkgs.mattermost}/bin/mattermost config migrate ${cfg.statePath}/config/config.json ${database}
         '' + lib.optionalString cfg.mutableConfig ''
           if ! test -e "${cfg.statePath}/config/.initial-created"; then
             rm -f ${cfg.statePath}/config/config.json
@@ -201,7 +207,8 @@ in
           PermissionsStartOnly = true;
           User = cfg.user;
           Group = cfg.group;
-          ExecStart = "${pkgs.mattermost}/bin/mattermost";
+          ExecStart = "${pkgs.mattermost}/bin/mattermost" +
+            (lib.optionalString (!cfg.mutableConfig) " -c ${database}");
           WorkingDirectory = "${cfg.statePath}";
           Restart = "always";
           RestartSec = "10";
@@ -227,4 +234,3 @@ in
     })
   ];
 }
-
diff --git a/pkgs/servers/mattermost/default.nix b/pkgs/servers/mattermost/default.nix
index 2919647e573..00f74e7a01e 100644
--- a/pkgs/servers/mattermost/default.nix
+++ b/pkgs/servers/mattermost/default.nix
@@ -1,7 +1,7 @@
 { stdenv, fetchurl, fetchFromGitHub, buildGoPackage, buildEnv }:
 
 let
-  version = "5.9.0";
+  version = "5.15.0";
 
   mattermost-server = buildGoPackage rec {
     pname = "mattermost-server";
@@ -11,7 +11,7 @@ let
       owner = "mattermost";
       repo = "mattermost-server";
       rev = "v${version}";
-      sha256 = "08h7n9smv6f1njazn4pl6pwkfmqxn93rzg69h6asicp9c4vad3m2";
+      sha256 = "1bh53h0bmpc1qmnbpsmwkfrvj66z18m7b1xg7pqikid57ssqxjx9";
     };
 
     goPackagePath = "github.com/mattermost/mattermost-server";
@@ -29,7 +29,7 @@ let
 
     src = fetchurl {
       url = "https://releases.mattermost.com/${version}/mattermost-${version}-linux-amd64.tar.gz";
-      sha256 = "19ys5mwmw99fbj44gd00vrl2qj09lrwvj1ihic0fsn6nd3hnx3mw";
+      sha256 = "13xmc2y4pp0b0svzaf4v7ynx6rxcvznx3vqmlrpiil414s69xv45";
     };
 
     installPhase = ''