diff --git a/src/Tiny_httpd_html.ml b/src/Tiny_httpd_html.ml
index 2ebf6b1b..52383ebd 100644
--- a/src/Tiny_httpd_html.ml
+++ b/src/Tiny_httpd_html.ml
@@ -1,4 +1,12 @@
 
+(** HTML combinators.
+
+    This module provides combinators to produce html. It doesn't enforce
+    the well-formedness of the html, unlike Tyxml, but it's simple and should
+    be reasonably efficient.
+    @since NEXT_RELEASE
+*)
+
 (** @inline *)
 include Tiny_httpd_html_
 
diff --git a/src/gen/gentags.ml b/src/gen/gentags.ml
index a2c8a461..9b6d3129 100644
--- a/src/gen/gentags.ml
+++ b/src/gen/gentags.ml
@@ -281,7 +281,10 @@ let prelude = {|
 (** Output for HTML combinators.
 
     This output type is used to produce a string reasonably efficiently from
-    a tree of combinators. *)
+    a tree of combinators.
+
+    @since NEXT_RELEASE
+    @open *)
 module Out : sig
   type t
   val create : unit -> t