diff --git a/nixos/modules/services/matrix/matrix-authentication-service.nix b/nixos/modules/services/matrix/matrix-authentication-service.nix
index 4b57643e4090..ee3c1a5d8232 100644
--- a/nixos/modules/services/matrix/matrix-authentication-service.nix
+++ b/nixos/modules/services/matrix/matrix-authentication-service.nix
@@ -45,7 +45,9 @@ let
       pruned;
   configFile = format.generate "config.yaml" finalSettings;
 
-  extraConfigFiles = lib.imap0 (i: _: "%d/config-${toString i}") cfg.extraConfigFiles;
+  extraConfigFiles = lib.imap0 (
+    i: _: "\${CREDENTIALS_DIRECTORY}/config-${toString i}"
+  ) cfg.extraConfigFiles;
   runtimeConfig = "/run/matrix-authentication-service/config.yaml";
 in
 {