diff --git a/specs/core/0_beacon-chain.md b/specs/core/0_beacon-chain.md
index 6f7a7a059..007079555 100644
--- a/specs/core/0_beacon-chain.md
+++ b/specs/core/0_beacon-chain.md
@@ -737,8 +737,7 @@ def get_randao_mix(state: BeaconState,
                    epoch: Epoch) -> Hash:
     """
     Return the randao mix at a recent ``epoch``.
-    ``epoch`` expected to be between (current_epoch - EPOCHS_PER_HISTORICAL_VECTOR, current_epoch], unless 
-    otherwise noted at a call site.
+    ``epoch`` expected to be between (current_epoch - EPOCHS_PER_HISTORICAL_VECTOR, current_epoch].
     """
     return state.randao_mixes[epoch % EPOCHS_PER_HISTORICAL_VECTOR]
 ```
@@ -763,12 +762,9 @@ def generate_seed(state: BeaconState,
                   epoch: Epoch) -> Hash:
     """
     Generate a seed for the given ``epoch``.
-    
-    Note that avoiding the underflow on ``get_randao_mix`` here violates
-    the epoch validity condition given in that function's comment.
     """
     return hash(
-        get_randao_mix(state, Epoch(epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD)) +
+        get_randao_mix(state, Epoch(epoch + EPOCHS_PER_HISTORICAL_VECTOR - MIN_SEED_LOOKAHEAD)) +  #avoid underflow
         get_active_index_root(state, epoch) +
         int_to_bytes(epoch, length=32)
     )