diff --git a/bin/main.ml b/bin/main.ml
index dfc6bac..f44b47f 100644
--- a/bin/main.ml
+++ b/bin/main.ml
@@ -15,8 +15,7 @@ let () =
   Log.debug "book is:\n  %s" (AddressBook.dump book);
   Log.debug "rules is:\n  %s" (List.map Rule.dump rules |> String.concat "\n  ");
   let scenarios =
-    List.map (fun rule -> Scenario.seq book rule) rules
-    |> List.map (fun seq -> Seq.take 10 seq |> List.of_seq)
+    List.map (fun rule -> Scenario.gen 10 book rule) rules
     |> List.concat
   in
   scenarios |> List.iter (fun scenario -> Log.debug "SC: %s" (Scenario.dump scenario));
diff --git a/bin/scenario.ml b/bin/scenario.ml
index 9082cc6..6383066 100644
--- a/bin/scenario.ml
+++ b/bin/scenario.ml
@@ -47,11 +47,14 @@ let gen_aux book rule : (string * string * string) Gen.t =
         return (src_ip, Ip.to_string dst, "")
      end
 
-let gen book rule =
+let gen n book rule =
   let desc idx = !%"%s-%04d" rule.Rule.name (idx+1) in
   gen_aux book rule
   |> Gen.to_seq
-  |> Seq.mapi (fun idx (src_ip, dst_ip, url_domain) ->
+  |> Seq.take n
+  |> List.of_seq
+  |> list_uniques
+  |> List.mapi (fun idx (src_ip, dst_ip, url_domain) ->
          {src_ip; dst_ip; url_domain; description=(desc idx)})
 
 let seq_addr addr =
diff --git a/lib/common.ml b/lib/common.ml
index 086cf59..4ed4f4b 100644
--- a/lib/common.ml
+++ b/lib/common.ml
@@ -22,6 +22,22 @@ let rec list_shuffle rand xs =
      | Some(x, xs) -> x :: list_shuffle rand xs
      | None -> []
 
+let rec elem x xs =
+  match xs with
+  | [] -> false
+  | y :: ys -> x = y || elem x ys
+
+let list_uniques l =
+  let rec helper l acc =
+    match l with
+    | [] -> acc
+    | x :: xs ->
+        if elem x acc then
+          helper xs acc
+        else
+          helper xs (x :: acc)
+  in List.rev (helper l [])
+
 module SeqMonad = struct
   type 'a t = 'a Seq.t