diff --git a/multiSet.ml b/multiSet.ml
index a896544f..41d147f8 100644
--- a/multiSet.ml
+++ b/multiSet.ml
@@ -31,6 +31,8 @@ module type S = sig
 
   val empty : t
 
+  val is_empty : t -> bool
+
   val mem : t -> elt -> bool
 
   val count : t -> elt -> int
@@ -78,6 +80,8 @@ module Make(O : Set.OrderedType) = struct
 
   let empty = M.empty
 
+  let is_empty = M.is_empty
+
   let mem ms x = M.mem x ms
 
   let count ms x =
diff --git a/multiSet.mli b/multiSet.mli
index e7979dfa..99e0521f 100644
--- a/multiSet.mli
+++ b/multiSet.mli
@@ -31,6 +31,8 @@ module type S = sig
 
   val empty : t
 
+  val is_empty : t -> bool
+
   val mem : t -> elt -> bool
 
   val count : t -> elt -> int