diff --git a/src/core/CCString.ml b/src/core/CCString.ml
index aadd9d9c..11291efe 100644
--- a/src/core/CCString.ml
+++ b/src/core/CCString.ml
@@ -81,6 +81,12 @@ let rev s =
   Q.printable_string (fun s -> length s = length (rev s))
 *)
 
+(*$Q
+  Q.printable_string (fun s -> \
+    rev s = (to_list s |> List.rev |> of_list))
+  *)
+
+
 (*$=
   "abc" (rev "cba")
   "" (rev "")
diff --git a/src/data/CCRingBuffer.ml b/src/data/CCRingBuffer.ml
index af64a188..7c2e88b7 100644
--- a/src/data/CCRingBuffer.ml
+++ b/src/data/CCRingBuffer.ml
@@ -200,7 +200,7 @@ end
   open Q.Gen
   let g_char = map Char.chr (Char.code 'A' -- Char.code 'z')
   let g_str = string_size ~gen:g_char (0--10)
-  let a_str = {Q.string with Q.gen=g_str}
+  let a_str = Q.set_gen g_str Q.string
 *)
 
 module MakeFromArray(A:Array.S) : S with module Array = A = struct