diff --git a/machines/renge/services/matrix/synapse.nix b/machines/renge/services/matrix/synapse.nix
index 8c63337..510dc9f 100644
--- a/machines/renge/services/matrix/synapse.nix
+++ b/machines/renge/services/matrix/synapse.nix
@@ -49,7 +49,7 @@ in
 
       # adapted from https://github.com/NixOS/nixpkgs/blob/7e10bf4327491a6ebccbe1aaa8e6c6c0aca4663a/nixos/modules/services/misc/matrix-synapse-log_config.yaml
       #  - set root.level to WARNING instead of INFO
-      logConfig = builtins.toJSON {
+      log_config = pkgs.writeText "log_config.yaml" (builtins.toJSON {
         version = 1;
 
         formatters.journal_fmt.format = "%(name)s: [%(request)s] %(message)s";
@@ -72,7 +72,7 @@ in
         };
 
         disable_existing_loggers = false;
-      };
+      });
 
       max_upload_size = "50M";