diff --git a/eth2/state_processing/src/common/verify_bitfield.rs b/eth2/state_processing/src/common/verify_bitfield.rs
index 570a240f1..886269a54 100644
--- a/eth2/state_processing/src/common/verify_bitfield.rs
+++ b/eth2/state_processing/src/common/verify_bitfield.rs
@@ -4,7 +4,7 @@ use types::*;
 ///
 /// Is title `verify_bitfield` in spec.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 pub fn verify_bitfield_length(bitfield: &Bitfield, committee_size: usize) -> bool {
     if bitfield.num_bytes() != ((committee_size + 7) / 8) {
         return false;
diff --git a/eth2/state_processing/src/per_block_processing.rs b/eth2/state_processing/src/per_block_processing.rs
index 1d729578e..df35e8c7e 100644
--- a/eth2/state_processing/src/per_block_processing.rs
+++ b/eth2/state_processing/src/per_block_processing.rs
@@ -38,7 +38,7 @@ const VERIFY_DEPOSIT_MERKLE_PROOFS: bool = false;
 /// Returns `Ok(())` if the block is valid and the state was successfully updated. Otherwise
 /// returns an error describing why the block was invalid or how the function failed to execute.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 pub fn per_block_processing<T: EthSpec>(
     state: &mut BeaconState<T>,
     block: &BeaconBlock,
@@ -53,7 +53,7 @@ pub fn per_block_processing<T: EthSpec>(
 /// Returns `Ok(())` if the block is valid and the state was successfully updated. Otherwise
 /// returns an error describing why the block was invalid or how the function failed to execute.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 pub fn per_block_processing_without_verifying_block_signature<T: EthSpec>(
     state: &mut BeaconState<T>,
     block: &BeaconBlock,
@@ -68,7 +68,7 @@ pub fn per_block_processing_without_verifying_block_signature<T: EthSpec>(
 /// Returns `Ok(())` if the block is valid and the state was successfully updated. Otherwise
 /// returns an error describing why the block was invalid or how the function failed to execute.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 fn per_block_processing_signature_optional<T: EthSpec>(
     mut state: &mut BeaconState<T>,
     block: &BeaconBlock,
@@ -77,7 +77,7 @@ fn per_block_processing_signature_optional<T: EthSpec>(
 ) -> Result<(), Error> {
     process_block_header(state, block, spec)?;
 
-    // Ensure the current and previous epoch cache is built.
+    // Ensure the current and previous epoch caches are built.
     state.build_committee_cache(RelativeEpoch::Previous, spec)?;
     state.build_committee_cache(RelativeEpoch::Current, spec)?;
 
@@ -427,7 +427,7 @@ pub fn process_deposits<T: EthSpec>(
 /// Returns `Ok(())` if the validation and state updates completed successfully, otherwise returns
 /// an `Err` describing the invalid object or cause of failure.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 pub fn process_exits<T: EthSpec>(
     state: &mut BeaconState<T>,
     voluntary_exits: &[VoluntaryExit],
@@ -459,7 +459,7 @@ pub fn process_exits<T: EthSpec>(
 /// Returns `Ok(())` if the validation and state updates completed successfully, otherwise returns
 /// an `Err` describing the invalid object or cause of failure.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 pub fn process_transfers<T: EthSpec>(
     state: &mut BeaconState<T>,
     transfers: &[Transfer],
diff --git a/eth2/state_processing/src/per_slot_processing.rs b/eth2/state_processing/src/per_slot_processing.rs
index ebab36ff7..97645ab8a 100644
--- a/eth2/state_processing/src/per_slot_processing.rs
+++ b/eth2/state_processing/src/per_slot_processing.rs
@@ -10,14 +10,14 @@ pub enum Error {
 
 /// Advances a state forward by one slot, performing per-epoch processing if required.
 ///
-/// Spec v0.5.1
+/// Spec v0.6.1
 pub fn per_slot_processing<T: EthSpec>(
     state: &mut BeaconState<T>,
     spec: &ChainSpec,
 ) -> Result<(), Error> {
     cache_state(state, spec)?;
 
-    if (state.slot + 1) % spec.slots_per_epoch == 0 {
+    if (state.slot > spec.genesis_slot) && ((state.slot + 1) % spec.slots_per_epoch == 0) {
         per_epoch_processing(state, spec)?;
     }