From e821476c07560c8810acc768bb30a7abd2d00e2b Mon Sep 17 00:00:00 2001
From: Danny Ryan <dannyjryan@gmail.com>
Date: Wed, 22 Jan 2020 11:27:45 -0700
Subject: [PATCH] explicitly use Optiona type for fork_version in
 compute_domain

Co-Authored-By: Carl Beekhuizen <carl@ethereum.org>
---
 scripts/build_spec.py        | 2 +-
 specs/phase0/beacon-chain.md | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/build_spec.py b/scripts/build_spec.py
index 114832bc2a..16dd0d21d1 100644
--- a/scripts/build_spec.py
+++ b/scripts/build_spec.py
@@ -31,7 +31,7 @@
 SSZObject = TypeVar('SSZObject', bound=SSZType)
 '''
 PHASE1_IMPORTS = '''from typing import (
-    Any, Dict, Set, Sequence, MutableSequence, NewType, Tuple, Union, TypeVar
+    Any, Dict, Set, Sequence, MutableSequence, NewType, Optional, Tuple, Union, TypeVar
 )
 from math import (
     log2,
diff --git a/specs/phase0/beacon-chain.md b/specs/phase0/beacon-chain.md
index 478a2daa12..7f2e873bfb 100644
--- a/specs/phase0/beacon-chain.md
+++ b/specs/phase0/beacon-chain.md
@@ -788,7 +788,7 @@ def compute_activation_exit_epoch(epoch: Epoch) -> Epoch:
 #### `compute_domain`
 
 ```python
-def compute_domain(domain_type: DomainType, fork_version: Version=None) -> Domain:
+def compute_domain(domain_type: DomainType, fork_version: Optional[Version]=None) -> Domain:
     """
     Return the domain for the ``domain_type`` and ``fork_version``.
     """