diff --git a/eth2/state_processing/src/per_block_processing/errors.rs b/eth2/state_processing/src/per_block_processing/errors.rs
index 6614f6f608..9c36e0238b 100644
--- a/eth2/state_processing/src/per_block_processing/errors.rs
+++ b/eth2/state_processing/src/per_block_processing/errors.rs
@@ -271,10 +271,10 @@ pub enum ProposerSlashingValidationError {
 pub enum ProposerSlashingInvalid {
     /// The proposer index is not a known validator.
     ProposerUnknown(u64),
-    /// The two proposal have different slots.
+    /// The two proposal have different epochs.
     ///
     /// (proposal_1_slot, proposal_2_slot)
-    ProposalSlotMismatch(Slot, Slot),
+    ProposalEpochMismatch(Slot, Slot),
     /// The proposals are identical and therefore not slashable.
     ProposalsIdentical,
     /// The specified proposer has already been slashed.
diff --git a/eth2/state_processing/src/per_block_processing/verify_proposer_slashing.rs b/eth2/state_processing/src/per_block_processing/verify_proposer_slashing.rs
index 8e0a70f963..b5113863e1 100644
--- a/eth2/state_processing/src/per_block_processing/verify_proposer_slashing.rs
+++ b/eth2/state_processing/src/per_block_processing/verify_proposer_slashing.rs
@@ -21,8 +21,9 @@ pub fn verify_proposer_slashing(
         })?;
 
     verify!(
-        proposer_slashing.header_1.slot == proposer_slashing.header_2.slot,
-        Invalid::ProposalSlotMismatch(
+        proposer_slashing.header_1.slot.epoch(spec.slots_per_epoch)
+            == proposer_slashing.header_2.slot.epoch(spec.slots_per_epoch),
+        Invalid::ProposalEpochMismatch(
             proposer_slashing.header_1.slot,
             proposer_slashing.header_2.slot
         )