diff --git a/src/util/IArray.ml b/src/util/IArray.ml
index 8884da4d..16b4d8af 100644
--- a/src/util/IArray.ml
+++ b/src/util/IArray.ml
@@ -165,6 +165,12 @@ let iter2 f a b =
     f (unsafe_get a i) (unsafe_get b i)
   done
 
+let iteri2 f a b =
+  if length a <> length b then invalid_arg "iteri2";
+  for i = 0 to length a-1 do
+    f i (unsafe_get a i) (unsafe_get b i)
+  done
+
 let fold2 f acc a b =
   if length a <> length b then invalid_arg "fold2";
   let rec aux acc i =
diff --git a/src/util/IArray.mli b/src/util/IArray.mli
index 8aff9543..19f103f2 100644
--- a/src/util/IArray.mli
+++ b/src/util/IArray.mli
@@ -106,5 +106,7 @@ val map2 : ('a -> 'b -> 'c) -> 'a t -> 'b t -> 'c t
 
 val fold2 : ('acc -> 'a -> 'b -> 'acc) -> 'acc -> 'a t -> 'b t -> 'acc
 
+val iteri2 : (int -> 'a -> 'b -> unit) -> 'a t -> 'b t -> unit
+
 val iter2 : ('a -> 'b -> unit) -> 'a t -> 'b t -> unit