diff --git a/nixos/modules/services/networking/tlsdated.nix b/nixos/modules/services/networking/tlsdated.nix
index ff7d0178a81..757cce28760 100644
--- a/nixos/modules/services/networking/tlsdated.nix
+++ b/nixos/modules/services/networking/tlsdated.nix
@@ -26,6 +26,7 @@ in
 
       extraOptions = mkOption {
         type = types.string;
+        default = "";
         description = ''
           Additional command line arguments to pass to tlsdated.
         '';