diff --git a/src/api_call.ml b/src/api_call.ml
index 66f5083..6e96e95 100644
--- a/src/api_call.ml
+++ b/src/api_call.ml
@@ -112,7 +112,7 @@ include
       include T
     end)
     (Open_on_rhs_intf)
-    ()
+    (struct end)
 
 module Or_error = struct
   type nonrec 'a t = 'a Or_error.t t
@@ -138,7 +138,7 @@ module Or_error = struct
         include T
       end)
       (Open_on_rhs_intf)
-      ()
+      (struct end)
 
   let error_s sexp = Const (Or_error.error_s sexp)
   let ignore_m t = map t ~f:ignore