diff --git a/nixos/modules/programs/rust-motd.nix b/nixos/modules/programs/rust-motd.nix
index 301b7cebb7f8..19f98868ee34 100644
--- a/nixos/modules/programs/rust-motd.nix
+++ b/nixos/modules/programs/rust-motd.nix
@@ -88,7 +88,7 @@ in {
   };
   config = lib.mkIf cfg.enable {
     assertions = [
-      { assertion = config.users.motd == null;
+      { assertion = config.users.motd == "";
         message = ''
           `programs.rust-motd` is incompatible with `users.motd`!
         '';