diff --git a/src/lib/structures/expr.mli b/src/lib/structures/expr.mli
index e8490cf48..c2281e53b 100644
--- a/src/lib/structures/expr.mli
+++ b/src/lib/structures/expr.mli
@@ -254,8 +254,9 @@ val real : string -> t
 val bitv : string -> Ty.t -> t
 val fresh_name : Ty.t -> t
 
-(* Special names used for AC(X) abstraction.
-   These corresponds to the K sort in the AC(X) paper. *)
+(** Special names used for AC(X) abstraction.
+    These corresponds to the K sort in the AC(X) paper. *)
+
 val fresh_ac_name : Ty.t -> t
 val is_fresh_ac_name : t -> bool