diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index d93cb21d7..dbc8db0e9 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -833,7 +833,7 @@ def get_next_epoch_committee_count(state: BeaconState) -> int:
 ```python
 def get_crosslink_committees_at_slot(state: BeaconState,
                                      slot: SlotNumber,
-                                     registry_change=False: bool) -> List[Tuple[List[ValidatorIndex], ShardNumber]]:
+                                     registry_change: bool=False) -> List[Tuple[List[ValidatorIndex], ShardNumber]]:
     """
     Return the list of ``(committee, shard)`` tuples for the ``slot``.
 
diff --git a/specs/validator/0_beacon-chain-validator.md b/specs/validator/0_beacon-chain-validator.md
index b01e7a3af..3df3d758d 100644
--- a/specs/validator/0_beacon-chain-validator.md
+++ b/specs/validator/0_beacon-chain-validator.md
@@ -345,15 +345,23 @@ Either (2) or (3) occurs if (1) fails. The choice between (2) and (3) is determi
 
 ```python
 def get_next_epoch_crosslink_committees(state: BeaconState,
-                                        validator_index: ValidatorIndex) -> List[Tuple[ValidatorIndex], ShardNumber]:
+                                        validator_index: ValidatorIndex) -> List[Tuple[List[ValidatorIndex], ShardNumber]]:
     current_epoch = get_current_epoch(state)
     next_epoch = current_epoch + 1
     next_epoch_start_slot = get_epoch_start_slot(next_epoch)
     potential_committees = []
-    for validator_registry in [False, True]:
+    for registry_change in [False, True]:
         for slot in range(next_epoch_start_slot, next_epoch_start_slot + EPOCH_LENGTH):
-            shard_committees = get_crosslink_committees_at_slot(state, slot, validator_registry)
-            selected_committees = [committee for committee in shard_committees if validator_index in committee[0]]
+            crosslink_committees = get_crosslink_committees_at_slot(
+                state,
+                slot,
+                registry_change=registry_change,
+            )
+            selected_committees = [
+                committee  # type: Tuple[List[ValidatorIndex], ShardNumber]
+                for committee in crosslink_committees
+                if validator_index in committee[0]
+            ]
             if len(selected_committees) > 0:
                 potential_assignments.append(selected_committees)
                 break