diff --git a/nixos/modules/services/matrix/dendrite.nix b/nixos/modules/services/matrix/dendrite.nix
index a5fea3da4844..a8006547fc6b 100644
--- a/nixos/modules/services/matrix/dendrite.nix
+++ b/nixos/modules/services/matrix/dendrite.nix
@@ -288,11 +288,11 @@ in
         LimitNOFILE = 65535;
         EnvironmentFile = lib.mkIf (cfg.environmentFile != null) cfg.environmentFile;
         LoadCredential = cfg.loadCredential;
-        ExecStartPre = ''
+        ExecStartPre = [''
           ${pkgs.envsubst}/bin/envsubst \
             -i ${configurationYaml} \
             -o /run/dendrite/dendrite.yaml
-        '';
+        ''];
         ExecStart = lib.strings.concatStringsSep " " ([
           "${pkgs.dendrite}/bin/dendrite-monolith-server"
           "--config /run/dendrite/dendrite.yaml"