diff --git a/zone-definition.nix b/zone-definition.nix
index af12e57..bf021fa 100644
--- a/zone-definition.nix
+++ b/zone-definition.nix
@@ -44,7 +44,7 @@ let
   };
 
   srvRecordEntry = {
-    options = {
+    options = with types; {
       host = mkOption {
         type = str;
         description = "Host providing service.";