diff --git a/src/core/route.mli b/src/core/route.mli
index 7d0c3980..c0c934b7 100644
--- a/src/core/route.mli
+++ b/src/core/route.mli
@@ -54,6 +54,8 @@ val to_string : _ t -> string
     @since 0.7 *)
 
 val to_url : ('a, string) t -> 'a
+(** [to_url route args] takes a route, and turns it into a URL path.
+    @since NEXT_RELEASE *)
 
 module Private_ : sig
   val eval : string list -> ('a, 'b) t -> 'a -> 'b option