diff --git a/eth2/state_processing/src/per_epoch_processing/process_slashings.rs b/eth2/state_processing/src/per_epoch_processing/process_slashings.rs
index b684dd33b..e9b814376 100644
--- a/eth2/state_processing/src/per_epoch_processing/process_slashings.rs
+++ b/eth2/state_processing/src/per_epoch_processing/process_slashings.rs
@@ -2,7 +2,7 @@ use types::{BeaconStateError as Error, *};
 
 /// Process slashings.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 pub fn process_slashings<T: EthSpec>(
     state: &mut BeaconState<T>,
     current_total_balance: u64,
@@ -24,10 +24,10 @@ pub fn process_slashings<T: EthSpec>(
             let penalty = std::cmp::max(
                 effective_balance * std::cmp::min(total_penalities * 3, current_total_balance)
                     / current_total_balance,
-                effective_balance / 1, /* FIXME(sproul): spec.min_penalty_quotient, */
+                effective_balance / spec.min_slashing_penalty_quotient,
             );
 
-            state.balances[index] -= penalty;
+            safe_sub_assign!(state.balances[index], penalty);
         }
     }