diff --git a/src/proto_alpha/lib_protocol/src/operation_repr.ml b/src/proto_alpha/lib_protocol/src/operation_repr.ml
index 9ed1d08ab..f9bdde259 100644
--- a/src/proto_alpha/lib_protocol/src/operation_repr.ml
+++ b/src/proto_alpha/lib_protocol/src/operation_repr.ml
@@ -468,9 +468,9 @@ module Encoding = struct
     (obj5
        (req "source" Contract_repr.encoding)
        (req "fee" Tez_repr.encoding)
-       (req "counter" (check_size 10 z))
-       (req "gas_limit" (check_size 10 z))
-       (req "storage_limit" (check_size 10 z)))
+       (req "counter" (check_size 10 n))
+       (req "gas_limit" (check_size 10 n))
+       (req "storage_limit" (check_size 10 n)))
 
   let extract
       (type kind)