diff --git a/src/lib_protocol_environment/tezos_protocol_environment.ml b/src/lib_protocol_environment/tezos_protocol_environment.ml
index 115eef828..89107729b 100644
--- a/src/lib_protocol_environment/tezos_protocol_environment.ml
+++ b/src/lib_protocol_environment/tezos_protocol_environment.ml
@@ -141,6 +141,7 @@ module Make (Context : CONTEXT) = struct
        and type RPC_service.meth = RPC_service.meth
        and type (+'m,'pr,'p,'q,'i,'o) RPC_service.t = ('m,'pr,'p,'q,'i,'o) RPC_service.t
        and type Error_monad.shell_error = Error_monad.error
+       and type Z.t = Z.t
 
     type error += Ecoproto_error of Error_monad.error
     val wrap_error : 'a Error_monad.tzresult -> 'a tzresult
diff --git a/src/lib_protocol_environment/tezos_protocol_environment.mli b/src/lib_protocol_environment/tezos_protocol_environment.mli
index e11bf40dd..8c9fc6710 100644
--- a/src/lib_protocol_environment/tezos_protocol_environment.mli
+++ b/src/lib_protocol_environment/tezos_protocol_environment.mli
@@ -134,6 +134,7 @@ module Make (Context : CONTEXT) : sig
        and type RPC_service.meth = RPC_service.meth
        and type (+'m,'pr,'p,'q,'i,'o) RPC_service.t = ('m,'pr,'p,'q,'i,'o) RPC_service.t
        and type Error_monad.shell_error = Error_monad.error
+       and type Z.t = Z.t
 
     type error += Ecoproto_error of Error_monad.error
     val wrap_error : 'a Error_monad.tzresult -> 'a tzresult