diff --git a/deployment/default.nix b/deployment/default.nix
index 3f8e550a..dbfa4610 100644
--- a/deployment/default.nix
+++ b/deployment/default.nix
@@ -38,8 +38,12 @@ panelConfigNullable:
 let
   inherit (lib) mkIf;
 
+  ## The convertor from module options to JSON schema does not generate proper
+  ## JSON schema types, forcing us to use nullable fields for default values.
+  ## However, working with those fields in the deployment code is annoying (and
+  ## unusual for Nix programmers), so we sanitize the input here and add back
+  ## the default value by hand.
   nonNull = x: v: if x == null then v else x;
-
   panelConfig = {
     domain = nonNull panelConfigNullable.domain "fediversity.net";
     initialUser = nonNull panelConfigNullable.initialUser {