diff --git a/lib/irc/mode.ml b/lib/irc/mode.ml
index 8c5f966..52b0dc1 100644
--- a/lib/irc/mode.ml
+++ b/lib/irc/mode.ml
@@ -249,7 +249,7 @@ let%expect_test _ =
 
   let print_set_nl s = Printf.printf "[%s]\n" (Set.to_string s) in
   let print_bool_nl b = print_endline (if b then "true" else "false") in
-  let print_change_nl c = Format.printf "%a\n" Set.pp_change c in
+  let print_change_nl c = Format.kasprintf print_string "%a\n" Set.pp_change c in
 
   print_set_nl Set.empty; [%expect {| [] |}];
   print_set_nl Set.(of_string "i"); [%expect {| [i] |}];
@@ -279,3 +279,27 @@ let%expect_test _ =
   let m, c = Set.normalize (Set.of_string "iw") (Parse.user_modes "-w+io") in
   Format.printf "%a -> [%a]" Set.pp_change c Set.pp m;
   [%expect {| +o-w -> [io] |}];
+
+  let print_chan_modes (m : Parse.chan_modes) =
+    Format.printf "[%a" Set.pp_change m.chan_modes;
+    begin match m.chan_limit with
+      | Some (`set n) -> Format.printf " +l:%d" n
+      | Some `unset -> Format.printf " -l"
+      | None -> ()
+    end;
+    begin match m.chan_key with
+      | Some (`set k) -> Format.printf " +k:%S" k
+      | Some `unset -> Format.printf " -k"
+      | None -> ()
+    end;
+    Format.printf "]\n@."
+  in
+
+  print_chan_modes (Parse.chan_modes "+im-nm+s" []);
+  [%expect {| [+is-mn] |}];
+
+  print_chan_modes (Parse.chan_modes "+l-ik+lt" ["100"; "*"; "200"]);
+  [%expect {| [+t-i +l:200 -k] |}];
+
+  print_chan_modes (Parse.chan_modes "+k-k+k" ["a"; "b"; "c"]);
+  [%expect {| [+ +k:"c"] |}];