diff --git a/beacon_node/beacon_chain/test_harness/specs/validator_registry.yaml b/beacon_node/beacon_chain/test_harness/specs/validator_registry.yaml
index 1674ecffc..ad9c899cf 100644
--- a/beacon_node/beacon_chain/test_harness/specs/validator_registry.yaml
+++ b/beacon_node/beacon_chain/test_harness/specs/validator_registry.yaml
@@ -48,7 +48,8 @@ test_cases:
         - slot: 63
           num_validators: 1003
           num_previous_epoch_attestations: 0
-          num_current_epoch_attestations: 10
+          # slots_per_epoch - attestation_inclusion_delay - skip_slots
+          num_current_epoch_attestations: 57
           slashed_validators: [11, 12, 13, 14, 42]
           exited_validators: []
           exit_initiated_validators: [50]
diff --git a/eth2/operation_pool/src/lib.rs b/eth2/operation_pool/src/lib.rs
index c42527b60..9d4d0091a 100644
--- a/eth2/operation_pool/src/lib.rs
+++ b/eth2/operation_pool/src/lib.rs
@@ -172,6 +172,8 @@ impl OperationPool {
                     || key.domain_bytes_match(&curr_domain_bytes)
             })
             .flat_map(|(_, attestations)| attestations)
+            // That are not superseded by an attestation included in the state...
+            .filter(|attestation| !superior_attestation_exists_in_state(state, attestation))
             // That are valid...
             .filter(|attestation| validate_attestation(state, attestation, spec).is_ok())
             // Scored by the number of new attestations they introduce (descending)
@@ -462,6 +464,31 @@ impl OperationPool {
     }
 }
 
+/// Returns `true` if the state already contains a `PendingAttestation` that is superior to the
+/// given `attestation`.
+///
+/// A validator has nothing to gain from re-including an attestation and it adds load to the
+/// network.
+///
+/// An existing `PendingAttestation` is superior to an existing `attestation` if:
+///
+/// - Their `AttestationData` is equal.
+/// - `attestation` does not contain any signatures that `PendingAttestation` does not have.
+fn superior_attestation_exists_in_state(state: &BeaconState, attestation: &Attestation) -> bool {
+    state
+        .current_epoch_attestations
+        .iter()
+        .chain(state.previous_epoch_attestations.iter())
+        .any(|existing_attestation| {
+            let bitfield = &attestation.aggregation_bitfield;
+            let existing_bitfield = &existing_attestation.aggregation_bitfield;
+
+            existing_attestation.data == attestation.data
+                && bitfield.intersection(existing_bitfield).num_set_bits()
+                    == bitfield.num_set_bits()
+        })
+}
+
 /// Filter up to a maximum number of operations out of an iterator.
 fn filter_limit_operations<'a, T: 'a, I, F>(operations: I, filter: F, limit: u64) -> Vec<T>
 where