diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index daa1bc108..36d45b31b 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -2102,7 +2102,9 @@ def update_validator_registry(state: BeaconState) -> None:
             activate_validator(state, index, is_genesis=False)
 
     # Exit validators within the allowable balance churn
-    balance_churn = 0
+    total_at_start = state.latest_slashed_balances[(current_epoch + 1) % LATEST_SLASHED_EXIT_LENGTH]
+    total_at_end = state.latest_slashed_balances[current_epoch % LATEST_SLASHED_EXIT_LENGTH]
+    balance_churn = total_at_end - total_at_start
     for index, validator in enumerate(state.validator_registry):
         if validator.exit_epoch == FAR_FUTURE_EPOCH and validator.initiated_exit:
             # Check the balance churn would be within the allowance