diff --git a/stylix/testbed.nix b/stylix/testbed.nix
index 469dd584..175c52b9 100644
--- a/stylix/testbed.nix
+++ b/stylix/testbed.nix
@@ -2,10 +2,10 @@
   pkgs,
   inputs,
   lib,
+  testbedFieldSeparator ? ":",
 }:
 
 let
-  testbedFieldSeparator = ":";
   username = "guest";
 
   commonModule =