diff --git a/eth2/types/src/fork.rs b/eth2/types/src/fork.rs
index d0decd737..eb4e183f2 100644
--- a/eth2/types/src/fork.rs
+++ b/eth2/types/src/fork.rs
@@ -37,13 +37,9 @@ impl Fork {
     ///
     /// Spec v0.6.1
     pub fn genesis(spec: &ChainSpec) -> Self {
-        let current_version: [u8; 4] = [0; 4];
-        // FIXME(sproul): 0 fork?
-        // current_version.copy_from_slice(&int_to_bytes4(spec.genesis_fork_version));
-
         Self {
-            previous_version: current_version,
-            current_version,
+            previous_version: [0; 4],
+            current_version: [0; 4],
             epoch: spec.genesis_epoch,
         }
     }
@@ -66,8 +62,7 @@ mod tests {
     ssz_tests!(Fork);
     cached_tree_hash_tests!(Fork);
 
-    // FIXME(sproul): dunno
-    fn test_genesis(version: u32, epoch: Epoch) {
+    fn test_genesis(epoch: Epoch) {
         let mut spec = ChainSpec::foundation();
 
         spec.genesis_epoch = epoch;
@@ -79,19 +74,14 @@ mod tests {
             fork.previous_version, fork.current_version,
             "previous and current are not identical"
         );
-        assert_eq!(
-            fork.current_version,
-            version.to_le_bytes(),
-            "current version incorrect"
-        );
     }
 
     #[test]
     fn genesis() {
-        test_genesis(0, Epoch::new(0));
-        test_genesis(9, Epoch::new(11));
-        test_genesis(2_u32.pow(31), Epoch::new(2_u64.pow(63)));
-        test_genesis(u32::max_value(), Epoch::max_value());
+        test_genesis(Epoch::new(0));
+        test_genesis(Epoch::new(11));
+        test_genesis(Epoch::new(2_u64.pow(63)));
+        test_genesis(Epoch::max_value());
     }
 
     #[test]
diff --git a/eth2/types/src/indexed_attestation.rs b/eth2/types/src/indexed_attestation.rs
index ab5364060..af294dfc1 100644
--- a/eth2/types/src/indexed_attestation.rs
+++ b/eth2/types/src/indexed_attestation.rs
@@ -58,8 +58,8 @@ mod tests {
 
     #[test]
     pub fn test_is_double_vote_true() {
-        let indexed_vote_first = create_indexed_attestation(1, 1);
-        let indexed_vote_second = create_indexed_attestation(1, 1);
+        let indexed_vote_first = create_indexed_attestation(3, 1);
+        let indexed_vote_second = create_indexed_attestation(3, 2);
 
         assert_eq!(
             indexed_vote_first.is_double_vote(&indexed_vote_second),
diff --git a/eth2/types/src/slashable_attestation.rs b/eth2/types/src/slashable_attestation.rs
deleted file mode 100644
index 19d9a87b6..000000000
--- a/eth2/types/src/slashable_attestation.rs
+++ /dev/null
@@ -1,151 +0,0 @@
-use crate::{test_utils::TestRandom, AggregateSignature, AttestationData, Bitfield, ChainSpec};
-
-use serde_derive::{Deserialize, Serialize};
-use ssz_derive::{Decode, Encode};
-use test_random_derive::TestRandom;
-use tree_hash::TreeHash;
-use tree_hash_derive::{CachedTreeHash, SignedRoot, TreeHash};
-
-/// Details an attestation that can be slashable.
-///
-/// To be included in an `AttesterSlashing`.
-///
-/// Spec v0.5.1
-#[derive(
-    Debug,
-    PartialEq,
-    Clone,
-    Serialize,
-    Deserialize,
-    Encode,
-    Decode,
-    TreeHash,
-    CachedTreeHash,
-    TestRandom,
-    SignedRoot,
-)]
-pub struct SlashableAttestation {
-    /// Lists validator registry indices, not committee indices.
-    pub validator_indices: Vec<u64>,
-    pub data: AttestationData,
-    pub custody_bitfield: Bitfield,
-    #[signed_root(skip_hashing)]
-    pub aggregate_signature: AggregateSignature,
-}
-
-impl SlashableAttestation {
-    /// Check if ``attestation_data_1`` and ``attestation_data_2`` have the same target.
-    ///
-    /// Spec v0.5.1
-    pub fn is_double_vote(&self, other: &SlashableAttestation, spec: &ChainSpec) -> bool {
-        self.data.slot.epoch(spec.slots_per_epoch) == other.data.slot.epoch(spec.slots_per_epoch)
-    }
-
-    /// Check if ``attestation_data_1`` surrounds ``attestation_data_2``.
-    ///
-    /// Spec v0.5.1
-    pub fn is_surround_vote(&self, other: &SlashableAttestation, spec: &ChainSpec) -> bool {
-        let source_epoch_1 = self.data.source_epoch;
-        let source_epoch_2 = other.data.source_epoch;
-        let target_epoch_1 = self.data.slot.epoch(spec.slots_per_epoch);
-        let target_epoch_2 = other.data.slot.epoch(spec.slots_per_epoch);
-
-        (source_epoch_1 < source_epoch_2) & (target_epoch_2 < target_epoch_1)
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use crate::chain_spec::ChainSpec;
-    use crate::slot_epoch::{Epoch, Slot};
-    use crate::test_utils::{SeedableRng, TestRandom, XorShiftRng};
-
-    #[test]
-    pub fn test_is_double_vote_true() {
-        let spec = ChainSpec::foundation();
-        let slashable_vote_first = create_slashable_attestation(1, 1, &spec);
-        let slashable_vote_second = create_slashable_attestation(1, 1, &spec);
-
-        assert_eq!(
-            slashable_vote_first.is_double_vote(&slashable_vote_second, &spec),
-            true
-        )
-    }
-
-    #[test]
-    pub fn test_is_double_vote_false() {
-        let spec = ChainSpec::foundation();
-        let slashable_vote_first = create_slashable_attestation(1, 1, &spec);
-        let slashable_vote_second = create_slashable_attestation(2, 1, &spec);
-
-        assert_eq!(
-            slashable_vote_first.is_double_vote(&slashable_vote_second, &spec),
-            false
-        );
-    }
-
-    #[test]
-    pub fn test_is_surround_vote_true() {
-        let spec = ChainSpec::foundation();
-        let slashable_vote_first = create_slashable_attestation(2, 1, &spec);
-        let slashable_vote_second = create_slashable_attestation(1, 2, &spec);
-
-        assert_eq!(
-            slashable_vote_first.is_surround_vote(&slashable_vote_second, &spec),
-            true
-        );
-    }
-
-    #[test]
-    pub fn test_is_surround_vote_true_realistic() {
-        let spec = ChainSpec::foundation();
-        let slashable_vote_first = create_slashable_attestation(4, 1, &spec);
-        let slashable_vote_second = create_slashable_attestation(3, 2, &spec);
-
-        assert_eq!(
-            slashable_vote_first.is_surround_vote(&slashable_vote_second, &spec),
-            true
-        );
-    }
-
-    #[test]
-    pub fn test_is_surround_vote_false_source_epoch_fails() {
-        let spec = ChainSpec::foundation();
-        let slashable_vote_first = create_slashable_attestation(2, 2, &spec);
-        let slashable_vote_second = create_slashable_attestation(1, 1, &spec);
-
-        assert_eq!(
-            slashable_vote_first.is_surround_vote(&slashable_vote_second, &spec),
-            false
-        );
-    }
-
-    #[test]
-    pub fn test_is_surround_vote_false_target_epoch_fails() {
-        let spec = ChainSpec::foundation();
-        let slashable_vote_first = create_slashable_attestation(1, 1, &spec);
-        let slashable_vote_second = create_slashable_attestation(2, 2, &spec);
-
-        assert_eq!(
-            slashable_vote_first.is_surround_vote(&slashable_vote_second, &spec),
-            false
-        );
-    }
-
-    ssz_tests!(SlashableAttestation);
-    cached_tree_hash_tests!(SlashableAttestation);
-
-    fn create_slashable_attestation(
-        slot_factor: u64,
-        source_epoch: u64,
-        spec: &ChainSpec,
-    ) -> SlashableAttestation {
-        let mut rng = XorShiftRng::from_seed([42; 16]);
-        let mut slashable_vote = SlashableAttestation::random_for_test(&mut rng);
-
-        slashable_vote.data.slot = Slot::new(slot_factor * spec.slots_per_epoch);
-        slashable_vote.data.source_epoch = Epoch::new(source_epoch);
-        slashable_vote
-    }
-}