diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index b9c3f5f0c..887ae6802 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -1294,7 +1294,7 @@ def process_justification_and_finalization(state: BeaconState) -> None:
 
     # Process justifications
     state.previous_justified_checkpoint = state.current_justified_checkpoint
-    state.justification_bits[1:] == state.justification_bits[:JUSTIFICATION_BITS_LENGTH - 1]
+    state.justification_bits[1:] = state.justification_bits[:JUSTIFICATION_BITS_LENGTH - 1]
     state.justification_bits[0] = 0b0
     matching_target_attestations = get_matching_target_attestations(state, previous_epoch)  # Previous epoch
     if get_attesting_balance(state, matching_target_attestations) * 3 >= get_total_active_balance(state) * 2:
diff --git a/test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py b/test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py
index 91d3ff4f2..d87a22399 100644
--- a/test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py
+++ b/test_libs/pyspec/eth2spec/utils/ssz/ssz_typing.py
@@ -325,7 +325,7 @@ class BaseList(list, Elements):
 
     def __setitem__(self, k, v):
         if type(k) == slice:
-            if k.start < 0 or k.stop > len(self):
+            if (k.start is not None and k.start < 0) or (k.stop is not None and k.stop > len(self)):
                 raise IndexError(f"cannot set item in type {self.__class__}"
                                  f" at out of bounds slice {k} (to {v}, bound: {len(self)})")
             super().__setitem__(k, [coerce_type_maybe(x, self.__class__.elem_type) for x in v])