diff --git a/nix/sources.json b/nix/sources.json
index 6f3b58c..f3e3440 100644
--- a/nix/sources.json
+++ b/nix/sources.json
@@ -23,7 +23,7 @@
         "homepage": "https://mattermost.com",
         "owner": "mattermost",
         "repo": "mattermost-server",
-        "rev": "3172adfce9d98fe8f9c98ccd0a0fdbb52291ae0a",
+        "rev": "8f352436049776b5bd7c006bb03992d8fe2f029f",
         "sha256": "1sy0kydp87pwby0whgq678jq1zpivqndip81787r9b3dqcyq47cp",
         "type": "tarball",
         "url": "https://github.com/mattermost/mattermost-server/archive/refs/tags/v6.1.2.tar.gz",
@@ -75,10 +75,10 @@
         "homepage": "",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "8a053bc2255659c5ca52706b9e12e76a8f50dbdd",
-        "sha256": "087lqvl8icvwzk61a0sn87m48a7bmm1bhna3v61w12ad97an9shj",
+        "rev": "6c4b9f1a2fd761e2d384ef86cff0d208ca27fdca",
+        "sha256": "1yl5gj0mzczhl1j8sl8iqpwa1jzsgr12fdszw9rq13cdig2a2r5f",
         "type": "tarball",
-        "url": "https://github.com/nixos/nixpkgs/archive/8a053bc2255659c5ca52706b9e12e76a8f50dbdd.tar.gz",
+        "url": "https://github.com/nixos/nixpkgs/archive/6c4b9f1a2fd761e2d384ef86cff0d208ca27fdca.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "nixpkgs-unstable": {
@@ -87,10 +87,10 @@
         "homepage": "",
         "owner": "nixos",
         "repo": "nixpkgs",
-        "rev": "5b091d4fbe3b7b7493c3b46fe0842e4b30ea24b3",
-        "sha256": "0yb7l5p4k9q8avwiq0fgp87ij50d6yavgh4dfw14jh2lf8daqbmp",
+        "rev": "945ec499041db73043f745fad3b2a3a01e826081",
+        "sha256": "1ixv310sjw0r5vda4yfwp3snyha2i9h7aqygd43cyvdk2qsjk8pq",
         "type": "tarball",
-        "url": "https://github.com/nixos/nixpkgs/archive/5b091d4fbe3b7b7493c3b46fe0842e4b30ea24b3.tar.gz",
+        "url": "https://github.com/nixos/nixpkgs/archive/945ec499041db73043f745fad3b2a3a01e826081.tar.gz",
         "url_template": "https://github.com/<owner>/<repo>/archive/<rev>.tar.gz"
     },
     "workadventure": {
diff --git a/services/hedgedoc-hacc.nix b/services/hedgedoc-hacc.nix
index f0287f5..430e4fb 100644
--- a/services/hedgedoc-hacc.nix
+++ b/services/hedgedoc-hacc.nix
@@ -44,6 +44,7 @@
           allowOrigin = [ "localhost" "pad.hacc.space" "fff-muc.de" ];
           db = {
             host = "/run/postgresql";
+            username = "codimd";
             dialect = "postgres";
             database = "codimd";
           };
@@ -80,7 +81,9 @@
         }];
         authentication = ''
           local all all trust
+          host  codimd  codimd  127.0.0.1/32  trust
         '';
+        package = pkgs.postgresql_11;
       };
       services.postgresqlBackup = {
         enable = true;
diff --git a/services/hedgedoc-i4f.nix b/services/hedgedoc-i4f.nix
index af3f6c8..4580b82 100644
--- a/services/hedgedoc-i4f.nix
+++ b/services/hedgedoc-i4f.nix
@@ -60,6 +60,7 @@
       };
       services.postgresql = {
         enable = true;
+        package = pkgs.postgresql_11;
         authentication = ''
           local all       all                     trust
           host  hedgedoc  hedgedoc  127.0.0.1/32  trust
diff --git a/services/mattermost.nix b/services/mattermost.nix
index a8e4b82..4e9e41b 100644
--- a/services/mattermost.nix
+++ b/services/mattermost.nix
@@ -202,6 +202,7 @@ in {
 
       services.postgresql = {
         enable = lib.mkForce true; # mattermost sets this to false. wtf.
+        package = pkgs.postgresql_11;
         ensureDatabases = [ "mattermost" ];
         ensureUsers = [ {
           name = "mattermost";
diff --git a/services/nextcloud/default.nix b/services/nextcloud/default.nix
index aaac896..484e0c6 100644
--- a/services/nextcloud/default.nix
+++ b/services/nextcloud/default.nix
@@ -102,6 +102,7 @@
 
       services.postgresql = {
         enable = true;
+        package = pkgs.postgresql_11;
         ensureDatabases = [ "nextcloud" ];
         ensureUsers = [
           { # by default, postgres has unix sockets enabled, and allows a