diff --git a/nixos/modules/services/web-apps/mattermost.nix b/nixos/modules/services/web-apps/mattermost.nix
index bf3a8eed600..8e6baf6a17e 100644
--- a/nixos/modules/services/web-apps/mattermost.nix
+++ b/nixos/modules/services/web-apps/mattermost.nix
@@ -202,6 +202,7 @@ in
           ExecStart = "${pkgs.mattermost}/bin/mattermost-platform";
           WorkingDirectory = "${cfg.statePath}";
           PrivateTmp = true;
+          JoinsNamespaceOf = mkIf cfg.localDatabaseCreate "postgresql.service";
           Restart = "always";
           RestartSec = "10";
           LimitNOFILE = "49152";