diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 139b8024b..ac73c08aa 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -577,7 +577,7 @@ The types are defined topologically to aid in facilitating an executable version
     # Randomness and committees
     'latest_randao_mixes': ['bytes32', LATEST_RANDAO_MIXES_LENGTH],
     'latest_start_shard': 'uint64',
-    
+
     # Finality
     'previous_epoch_attestations': [PendingAttestation],
     'current_epoch_attestations': [PendingAttestation],
@@ -651,7 +651,7 @@ Note: We aim to migrate to a S[T/N]ARK-friendly hash function in a future Ethere
 ```python
 def get_temporary_block_header(block: BeaconBlock) -> BeaconBlockHeader:
     """
-    Return the block header corresponding to a block with ``state_root`` set to ``ZERO_HASH``. 
+    Return the block header corresponding to a block with ``state_root`` set to ``ZERO_HASH``.
     """
     return BeaconBlockHeader(
         slot=block.slot,
@@ -796,7 +796,7 @@ def get_permuted_index(index: int, list_size: int, seed: Bytes32) -> int:
     """
     assert index < list_size
     assert list_size <= 2**40
-    
+
     for round in range(SHUFFLE_ROUND_COUNT):
         pivot = bytes_to_int(hash(seed + int_to_bytes1(round))[0:8]) % list_size
         flip = (pivot - index) % list_size
@@ -1659,7 +1659,7 @@ def get_winning_crosslink_and_attesting_indices(state: BeaconState, epoch: Epoch
     ) for a in pending_attestations if a.data.shard == shard]
 
     if len(candidate_crosslinks) == 0:
-        return Crosslink(GENESIS_EPOCH, ZERO_HASH, ZERO_HASH), []
+        return Crosslink(epoch=GENESIS_EPOCH, crosslink_data_root=ZERO_HASH, previous_crosslink_root=ZERO_HASH), []
 
     def get_attestations_for(crosslink_data_root) -> List[PendingAttestation]:
         return [a for a in pending_attestations if a.data.shard == shard and a.data.crosslink_data_root == crosslink_data_root]
@@ -1899,7 +1899,7 @@ def update_registry(state: BeaconState) -> None:
     ], key=lambda index: state.validator_registry[index].activation_eligibility_epoch)
 
     for index in activation_queue[:get_churn_limit(state)]:
-        activate_validator(state, index, is_genesis=False) 
+        activate_validator(state, index, is_genesis=False)
 
     state.latest_start_shard = (
         state.latest_start_shard +
diff --git a/specs/core/1_custody-game.md b/specs/core/1_custody-game.md
index 138e69fee..74b086219 100644
--- a/specs/core/1_custody-game.md
+++ b/specs/core/1_custody-game.md
@@ -309,7 +309,7 @@ def process_chunk_challenge(state: BeaconState,
     responder = state.validator_registry[challenge.responder_index]
     assert responder.exit_epoch >= get_current_epoch(state) - MAX_CHUNK_CHALLENGE_DELAY
     # Verify the responder participated in the attestation
-    attesters = get_attestation_participants(state, attestation.data, attestation.aggregation_bitfield)
+    attesters = get_attesting_indices(state, attestation.data, attestation.aggregation_bitfield)
     assert challenge.responder_index in attesters
     # Verify the challenge is not a duplicate
     for record in state.custody_chunk_challenge_records:
@@ -359,9 +359,9 @@ def process_bit_challenge(state: BeaconState,
     # Verify the attestation is eligible for challenging
     responder = state.validator_registry[challenge.responder_index]
     min_challengeable_epoch = responder.exit_epoch - EPOCHS_PER_CUSTODY_PERIOD * (1 + responder.max_reveal_lateness)
-    assert min_challengeable_epoch <= slot_to_epoch(challenge.attestation.data.slot) 
+    assert min_challengeable_epoch <= slot_to_epoch(challenge.attestation.data.slot)
     # Verify the responder participated in the attestation
-    attesters = get_attestation_participants(state, attestation.data, attestation.aggregation_bitfield)
+    attesters = get_attesting_indices(state, attestation.data, attestation.aggregation_bitfield)
     assert challenge.responder_index in attesters
     # A validator can be the challenger or responder for at most one challenge at a time
     for record in state.custody_bit_challenge_records:
diff --git a/specs/validator/0_beacon-chain-validator.md b/specs/validator/0_beacon-chain-validator.md
index 53712880c..632bf2b62 100644
--- a/specs/validator/0_beacon-chain-validator.md
+++ b/specs/validator/0_beacon-chain-validator.md
@@ -299,7 +299,7 @@ Set `attestation.data = attestation_data` where `attestation_data` is the `Attes
 * Set `aggregation_bitfield[index_into_committee // 8] |= 2 ** (index_into_committee % 8)`.
 * Set `attestation.aggregation_bitfield = aggregation_bitfield`.
 
-_Note_: Calling `get_attestation_participants(state, attestation.data, attestation.aggregation_bitfield)` should return a list of length equal to 1, containing `validator_index`.
+_Note_: Calling `get_attesting_indices(state, attestation.data, attestation.aggregation_bitfield)` should return a list of length equal to 1, containing `validator_index`.
 
 ##### Custody bitfield
 
diff --git a/test_libs/pyspec/tests/helpers.py b/test_libs/pyspec/tests/helpers.py
index fca9d3bd0..384490d83 100644
--- a/test_libs/pyspec/tests/helpers.py
+++ b/test_libs/pyspec/tests/helpers.py
@@ -25,7 +25,7 @@ from eth2spec.phase0.spec import (
     # functions
     convert_to_indexed,
     get_active_validator_indices,
-    get_attestation_participants,
+    get_attesting_indices,
     get_block_root,
     get_crosslink_committee_for_attestation,
     get_current_epoch,
@@ -300,7 +300,7 @@ def get_valid_attestation(state, slot=None):
         custody_bitfield=custody_bitfield,
         aggregate_signature=EMPTY_SIGNATURE,
     )
-    participants = get_attestation_participants(
+    participants = get_attesting_indices(
         state,
         attestation.data,
         attestation.aggregation_bitfield,