diff --git a/src/backend/coq.ml b/src/backend/coq.ml
index 235f2b27..360f15fd 100644
--- a/src/backend/coq.ml
+++ b/src/backend/coq.ml
@@ -71,8 +71,8 @@ module Make(S : Res.S)(A : Arg with type hyp := S.clause
   let resolution fmt goal hyp1 hyp2 atom =
     let a = S.St.(atom.var.pa) in
     let h1, h2 =
-      if Array.memq a hyp1.S.St.atoms then hyp1, hyp2
-      else (assert (Array.memq a hyp2.S.St.atoms); hyp2, hyp1)
+      if Array_util.exists ((==) a) hyp1.S.St.atoms then hyp1, hyp2
+      else (assert (Array_util.exists ((==) a) hyp2.S.St.atoms); hyp2, hyp1)
     in
     (** Print some debug info *)
     Format.fprintf fmt