diff --git a/ocaml/tests/test_cluster.ml b/ocaml/tests/test_cluster.ml
index 07a857d20e..b42621a300 100644
--- a/ocaml/tests/test_cluster.ml
+++ b/ocaml/tests/test_cluster.ml
@@ -97,7 +97,7 @@ let test_rpc ~__context call =
       Rpc.{success= true; contents= Rpc.String ""; is_notification= false}
   | "Cluster.cstack_sync", [_session; self] ->
       let open API in
-      Xapi_cluster.cstack_sync ~__context ~self:(ref_Cluster_of_rpc self);
+      Xapi_cluster.cstack_sync ~__context ~self:(ref_Cluster_of_rpc self) ;
       Rpc.{success= true; contents= Rpc.String ""; is_notification= false}
   | name, params ->
       Alcotest.failf "Unexpected RPC: %s(%s)" name