diff --git a/nixos/modules/services/networking/radvd.nix b/nixos/modules/services/networking/radvd.nix
index f4b00c9b356..53fac4b7b72 100644
--- a/nixos/modules/services/networking/radvd.nix
+++ b/nixos/modules/services/networking/radvd.nix
@@ -33,6 +33,7 @@ in
     };
 
     services.radvd.config = mkOption {
+      type = types.lines;
       example =
         ''
           interface eth0 {