diff --git a/scripts/build_spec.py b/scripts/build_spec.py
index 9232cf00b..a16fa79ac 100644
--- a/scripts/build_spec.py
+++ b/scripts/build_spec.py
@@ -25,8 +25,6 @@ from dataclasses import (
     field,
 )
 
-from copy import deepcopy
-
 from eth2spec.utils.ssz.ssz_impl import (
     hash_tree_root,
     signing_root,
@@ -60,8 +58,6 @@ from dataclasses import (
     field,
 )
 
-from copy import deepcopy
-
 from eth2spec.utils.ssz.ssz_impl import (
     hash_tree_root,
     signing_root,
diff --git a/specs/core/0_fork-choice.md b/specs/core/0_fork-choice.md
index 5a4a52db4..ba97398a2 100644
--- a/specs/core/0_fork-choice.md
+++ b/specs/core/0_fork-choice.md
@@ -86,7 +86,8 @@ def get_genesis_store(genesis_state: BeaconState) -> Store:
         blocks={root: genesis_block},
         states={root: genesis_state},
         time=genesis_state.genesis_time,
-        justified_root=root, finalized_root=root,
+        justified_root=root,
+        finalized_root=root,
     )
 ```
 
@@ -143,7 +144,7 @@ def on_block(store: Store, block: BeaconBlock) -> None:
     # Check block is a descendant of the finalized block
     assert get_ancestor(store, signing_root(block), store.blocks[store.finalized_root].slot) == store.finalized_root
     # Check block slot against Unix time
-    pre_state = deepcopy(store.states[block.parent_root])
+    pre_state = store.states[block.parent_root].copy()
     assert store.time >= pre_state.genesis_time + block.slot * SECONDS_PER_SLOT
     # Check the block is valid and compute the post-state
     state = state_transition(pre_state, block)
diff --git a/test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py b/test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py
index 64d50b579..077f94b49 100644
--- a/test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py
+++ b/test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py
@@ -1,3 +1,4 @@
+import copy
 from types import GeneratorType
 from typing import (
     List,
@@ -151,6 +152,9 @@ class Container(object):
     def __hash__(self):
         return hash(self.hash_tree_root())
 
+    def copy(self):
+        return copy.deepcopy(self)
+
     @classmethod
     def get_fields_dict(cls):
         return dict(cls.__annotations__)