diff --git a/beacon_node/beacon_chain/src/beacon_block_reward.rs b/beacon_node/beacon_chain/src/beacon_block_reward.rs
index d345e6f5599..7eaaa3da702 100644
--- a/beacon_node/beacon_chain/src/beacon_block_reward.rs
+++ b/beacon_node/beacon_chain/src/beacon_block_reward.rs
@@ -82,7 +82,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
                     BeaconChainError::BlockRewardAttestationError
                 })?
         } else {
-            self.compute_beacon_block_attestation_reward_altair_deneb(block, state)
+            self.compute_beacon_block_attestation_reward_altair_and_later(block, state)
                 .map_err(|e| {
                     error!(
                         error = ?e,
@@ -249,7 +249,7 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         Ok(block_reward)
     }
 
-    fn compute_beacon_block_attestation_reward_altair_deneb<
+    fn compute_beacon_block_attestation_reward_altair_and_later<
         Payload: AbstractExecPayload<T::EthSpec>,
     >(
         &self,
@@ -267,13 +267,20 @@ impl<T: BeaconChainTypes> BeaconChain<T> {
         let mut previous_epoch_participation =
             state.previous_epoch_participation()?.to_owned_list();
 
+        let parent_slot = state
+            .latest_execution_payload_bid()
+            .ok()
+            .map(|bid| bid.slot);
+
         for attestation in block.body().attestations() {
             let data = attestation.data();
             let inclusion_delay = state.slot().safe_sub(data.slot)?.as_u64();
+
             // [Modified in Deneb:EIP7045]
             let participation_flag_indices = get_attestation_participation_flag_indices(
                 state,
                 data,
+                parent_slot,
                 inclusion_delay,
                 &self.spec,
             )?;
diff --git a/beacon_node/beacon_chain/src/validator_monitor.rs b/beacon_node/beacon_chain/src/validator_monitor.rs
index 294f160b821..8cca7a416ad 100644
--- a/beacon_node/beacon_chain/src/validator_monitor.rs
+++ b/beacon_node/beacon_chain/src/validator_monitor.rs
@@ -728,10 +728,16 @@ impl<E: EthSpec> ValidatorMonitor<E> {
 
                 let data = unaggregated_attestation.data();
 
+                let parent_slot = state
+                    .latest_execution_payload_bid()
+                    .ok()
+                    .map(|bid| bid.slot);
+
                 // Get the reward indices for the unaggregated attestation or log an error
                 match get_attestation_participation_flag_indices(
                     state,
                     unaggregated_attestation.data(),
+                    parent_slot,
                     inclusion_delay,
                     spec,
                 ) {
diff --git a/beacon_node/operation_pool/src/attestation.rs b/beacon_node/operation_pool/src/attestation.rs
index 7b6985b4c33..60bd2f2df9d 100644
--- a/beacon_node/operation_pool/src/attestation.rs
+++ b/beacon_node/operation_pool/src/attestation.rs
@@ -81,9 +81,19 @@ impl<'a, E: EthSpec> AttMaxCover<'a, E> {
         let att_data = att.attestation_data();
 
         let inclusion_delay = state.slot().as_u64().checked_sub(att_data.slot.as_u64())?;
-        let att_participation_flags =
-            get_attestation_participation_flag_indices(state, &att_data, inclusion_delay, spec)
-                .ok()?;
+        let parent_slot = state
+            .latest_execution_payload_bid()
+            .ok()
+            .map(|bid| bid.slot);
+
+        let att_participation_flags = get_attestation_participation_flag_indices(
+            state,
+            &att_data,
+            parent_slot,
+            inclusion_delay,
+            spec,
+        )
+        .ok()?;
 
         let fresh_validators_rewards = att
             .indexed
diff --git a/consensus/state_processing/src/common/get_attestation_participation.rs b/consensus/state_processing/src/common/get_attestation_participation.rs
index 8f1f000f401..ac27579d058 100644
--- a/consensus/state_processing/src/common/get_attestation_participation.rs
+++ b/consensus/state_processing/src/common/get_attestation_participation.rs
@@ -2,7 +2,7 @@ use integer_sqrt::IntegerSquareRoot;
 use safe_arith::SafeArith;
 use smallvec::SmallVec;
 use types::{
-    AttestationData, BeaconState, BeaconStateError as Error, ChainSpec, EthSpec,
+    AttestationData, BeaconState, BeaconStateError as Error, ChainSpec, EthSpec, Slot,
     consts::altair::{
         NUM_FLAG_INDICES, TIMELY_HEAD_FLAG_INDEX, TIMELY_SOURCE_FLAG_INDEX,
         TIMELY_TARGET_FLAG_INDEX,
@@ -21,6 +21,7 @@ use types::{
 pub fn get_attestation_participation_flag_indices<E: EthSpec>(
     state: &BeaconState<E>,
     data: &AttestationData,
+    parent_slot: Option<Slot>,
     inclusion_delay: u64,
     spec: &ChainSpec,
 ) -> Result<SmallVec<[usize; NUM_FLAG_INDICES]>, Error> {
@@ -37,6 +38,8 @@ pub fn get_attestation_participation_flag_indices<E: EthSpec>(
 
     // [New in Gloas:EIP7732]
     let payload_matches = if state.fork_name_unchecked().gloas_enabled() {
+        let parent_slot = parent_slot.ok_or(Error::MissingParentSlot)?;
+
         if state.is_attestation_same_slot(data)? {
             // For same-slot attestations, data.index must be 0
             if data.index != 0 {
@@ -45,8 +48,7 @@ pub fn get_attestation_participation_flag_indices<E: EthSpec>(
             true
         } else {
             // For non same-slot attestations, check execution payload availability
-            let slot_index = data
-                .slot
+            let slot_index = parent_slot
                 .as_usize()
                 .safe_rem(E::slots_per_historical_root())?;
             let payload_index = state
diff --git a/consensus/state_processing/src/per_block_processing.rs b/consensus/state_processing/src/per_block_processing.rs
index 22ec9a9ed47..2895ab756a9 100644
--- a/consensus/state_processing/src/per_block_processing.rs
+++ b/consensus/state_processing/src/per_block_processing.rs
@@ -185,6 +185,7 @@ pub fn per_block_processing<E: EthSpec, Payload: AbstractExecPayload<E>>(
     state.build_committee_cache(RelativeEpoch::Previous, spec)?;
     state.build_committee_cache(RelativeEpoch::Current, spec)?;
 
+    let mut parent_slot = None;
     // The call to the `process_execution_payload` must happen before the call to the
     // `process_randao` as the former depends on the `randao_mix` computed with the reveal of the
     // previous block.
@@ -193,6 +194,7 @@ pub fn per_block_processing<E: EthSpec, Payload: AbstractExecPayload<E>>(
         if state.fork_name_unchecked().gloas_enabled() {
             withdrawals::gloas::process_withdrawals::<E>(state, spec)?;
             let signed_bid = block.body().signed_execution_payload_bid()?;
+            parent_slot = Some(state.latest_execution_payload_bid()?.slot);
             process_execution_payload_bid(state, signed_bid, verify_signatures, spec)?;
         } else {
             if state.fork_name_unchecked().capella_enabled() {
@@ -208,7 +210,14 @@ pub fn per_block_processing<E: EthSpec, Payload: AbstractExecPayload<E>>(
 
     process_randao(state, block, verify_randao, ctxt, spec)?;
     process_eth1_data(state, block.body().eth1_data())?;
-    process_operations(state, block.body(), verify_signatures, ctxt, spec)?;
+    process_operations(
+        state,
+        block.body(),
+        verify_signatures,
+        parent_slot,
+        ctxt,
+        spec,
+    )?;
 
     if let Ok(sync_aggregate) = block.body().sync_aggregate() {
         process_sync_aggregate(
diff --git a/consensus/state_processing/src/per_block_processing/process_operations.rs b/consensus/state_processing/src/per_block_processing/process_operations.rs
index b2d2d49a83b..1b8af3d09e7 100644
--- a/consensus/state_processing/src/per_block_processing/process_operations.rs
+++ b/consensus/state_processing/src/per_block_processing/process_operations.rs
@@ -17,6 +17,7 @@ pub fn process_operations<E: EthSpec, Payload: AbstractExecPayload<E>>(
     state: &mut BeaconState<E>,
     block_body: BeaconBlockBodyRef<E, Payload>,
     verify_signatures: VerifySignatures,
+    parent_slot: Option<Slot>,
     ctxt: &mut ConsensusContext<E>,
     spec: &ChainSpec,
 ) -> Result<(), BlockProcessingError> {
@@ -40,7 +41,14 @@ pub fn process_operations<E: EthSpec, Payload: AbstractExecPayload<E>>(
         ctxt,
         spec,
     )?;
-    process_attestations(state, block_body, verify_signatures, ctxt, spec)?;
+    process_attestations(
+        state,
+        block_body,
+        verify_signatures,
+        parent_slot,
+        ctxt,
+        spec,
+    )?;
     process_deposits(state, &block_body.deposits().to_cow_slice(), spec)?;
     process_exits(
         state,
@@ -247,7 +255,7 @@ pub mod altair_deneb {
         let data = attestation.data();
         let inclusion_delay = state.slot().safe_sub(data.slot)?.as_u64();
         let participation_flag_indices =
-            get_attestation_participation_flag_indices(state, data, inclusion_delay, spec)?;
+            get_attestation_participation_flag_indices(state, data, None, inclusion_delay, spec)?;
 
         // Update epoch participation flags.
         let mut proposer_reward_numerator = 0;
@@ -304,6 +312,7 @@ pub mod gloas {
         state: &mut BeaconState<E>,
         attestations: I,
         verify_signatures: VerifySignatures,
+        parent_slot: Option<Slot>,
         ctxt: &mut ConsensusContext<E>,
         spec: &ChainSpec,
     ) -> Result<(), BlockProcessingError>
@@ -311,7 +320,15 @@ pub mod gloas {
         I: Iterator<Item = AttestationRef<'a, E>>,
     {
         attestations.enumerate().try_for_each(|(i, attestation)| {
-            process_attestation(state, attestation, i, ctxt, verify_signatures, spec)
+            process_attestation(
+                state,
+                attestation,
+                i,
+                verify_signatures,
+                parent_slot,
+                ctxt,
+                spec,
+            )
         })
     }
 
@@ -319,8 +336,9 @@ pub mod gloas {
         state: &mut BeaconState<E>,
         attestation: AttestationRef<E>,
         att_index: usize,
-        ctxt: &mut ConsensusContext<E>,
         verify_signatures: VerifySignatures,
+        parent_slot: Option<Slot>,
+        ctxt: &mut ConsensusContext<E>,
         spec: &ChainSpec,
     ) -> Result<(), BlockProcessingError> {
         let proposer_index = ctxt.get_proposer_index(state, spec)?;
@@ -339,8 +357,13 @@ pub mod gloas {
         // Matching roots, participation flag indices
         let data = attestation.data();
         let inclusion_delay = state.slot().safe_sub(data.slot)?.as_u64();
-        let participation_flag_indices =
-            get_attestation_participation_flag_indices(state, data, inclusion_delay, spec)?;
+        let participation_flag_indices = get_attestation_participation_flag_indices(
+            state,
+            data,
+            parent_slot,
+            inclusion_delay,
+            spec,
+        )?;
 
         // [New in EIP-7732]
         let current_epoch_target = data.target.epoch == state.current_epoch();
@@ -540,6 +563,7 @@ pub fn process_attestations<E: EthSpec, Payload: AbstractExecPayload<E>>(
     state: &mut BeaconState<E>,
     block_body: BeaconBlockBodyRef<E, Payload>,
     verify_signatures: VerifySignatures,
+    parent_slot: Option<Slot>,
     ctxt: &mut ConsensusContext<E>,
     spec: &ChainSpec,
 ) -> Result<(), BlockProcessingError> {
@@ -548,6 +572,7 @@ pub fn process_attestations<E: EthSpec, Payload: AbstractExecPayload<E>>(
             state,
             block_body.attestations(),
             verify_signatures,
+            parent_slot,
             ctxt,
             spec,
         )?;
diff --git a/consensus/state_processing/src/per_block_processing/tests.rs b/consensus/state_processing/src/per_block_processing/tests.rs
index 63f33548fb2..4b21c108963 100644
--- a/consensus/state_processing/src/per_block_processing/tests.rs
+++ b/consensus/state_processing/src/per_block_processing/tests.rs
@@ -441,10 +441,15 @@ async fn invalid_attestation_no_committee_for_index() {
         .into_data_mut()
         .index += 1;
     let mut ctxt = ConsensusContext::new(state.slot());
+    let parent_slot = state
+        .latest_execution_payload_bid()
+        .ok()
+        .map(|bid| bid.slot);
     let result = process_operations::process_attestations(
         &mut state,
         head_block.body(),
         VerifySignatures::True,
+        parent_slot,
         &mut ctxt,
         &spec,
     );
@@ -491,10 +496,15 @@ async fn invalid_attestation_wrong_justified_checkpoint() {
         .source = new_justified_checkpoint;
 
     let mut ctxt = ConsensusContext::new(state.slot());
+    let parent_slot = state
+        .latest_execution_payload_bid()
+        .ok()
+        .map(|bid| bid.slot);
     let result = process_operations::process_attestations(
         &mut state,
         head_block.body(),
         VerifySignatures::True,
+        parent_slot,
         &mut ctxt,
         &spec,
     );
@@ -545,10 +555,15 @@ async fn invalid_attestation_bad_aggregation_bitfield_len() {
     }
 
     let mut ctxt = ConsensusContext::new(state.slot());
+    let parent_slot = state
+        .latest_execution_payload_bid()
+        .ok()
+        .map(|bid| bid.slot);
     let result = process_operations::process_attestations(
         &mut state,
         head_block.body(),
         VerifySignatures::True,
+        parent_slot,
         &mut ctxt,
         &spec,
     );
@@ -585,10 +600,15 @@ async fn invalid_attestation_bad_signature() {
         .into_signature_mut() = AggregateSignature::empty();
 
     let mut ctxt = ConsensusContext::new(state.slot());
+    let parent_slot = state
+        .latest_execution_payload_bid()
+        .ok()
+        .map(|bid| bid.slot);
     let result = process_operations::process_attestations(
         &mut state,
         head_block.body(),
         VerifySignatures::True,
+        parent_slot,
         &mut ctxt,
         &spec,
     );
@@ -629,10 +649,15 @@ async fn invalid_attestation_included_too_early() {
         .slot = new_attesation_slot;
 
     let mut ctxt = ConsensusContext::new(state.slot());
+    let parent_slot = state
+        .latest_execution_payload_bid()
+        .ok()
+        .map(|bid| bid.slot);
     let result = process_operations::process_attestations(
         &mut state,
         head_block.body(),
         VerifySignatures::True,
+        parent_slot,
         &mut ctxt,
         &spec,
     );
@@ -680,10 +705,15 @@ async fn invalid_attestation_target_epoch_slot_mismatch() {
         .epoch += Epoch::new(1);
 
     let mut ctxt = ConsensusContext::new(state.slot());
+    let parent_slot = state
+        .latest_execution_payload_bid()
+        .ok()
+        .map(|bid| bid.slot);
     let result = process_operations::process_attestations(
         &mut state,
         head_block.body(),
         VerifySignatures::True,
+        parent_slot,
         &mut ctxt,
         &spec,
     );
diff --git a/consensus/state_processing/src/upgrade/altair.rs b/consensus/state_processing/src/upgrade/altair.rs
index 66bdb1af250..887fc100022 100644
--- a/consensus/state_processing/src/upgrade/altair.rs
+++ b/consensus/state_processing/src/upgrade/altair.rs
@@ -25,7 +25,7 @@ pub fn translate_participation<E: EthSpec>(
 
         // Translate attestation inclusion info to flag indices.
         let participation_flag_indices =
-            get_attestation_participation_flag_indices(state, data, inclusion_delay, spec)?;
+            get_attestation_participation_flag_indices(state, data, None, inclusion_delay, spec)?;
 
         // Apply flags to all attesting validators.
         let committee = state.get_beacon_committee(data.slot, data.index)?;
diff --git a/consensus/types/src/state/beacon_state.rs b/consensus/types/src/state/beacon_state.rs
index b70b1c5b21e..84e3b303a16 100644
--- a/consensus/types/src/state/beacon_state.rs
+++ b/consensus/types/src/state/beacon_state.rs
@@ -237,6 +237,7 @@ pub enum BeaconStateError {
     InvalidIndicesCount,
     InvalidBuilderPendingPaymentsIndex(usize),
     InvalidExecutionPayloadAvailabilityIndex(usize),
+    MissingParentSlot,
     /// Merkle proofs against the `BeaconState` and `BeaconBlockBody` use progressive-container
     /// generalized indices from Gloas (EIP-7688) onwards, which are not implemented yet.
     ProgressiveMerkleProofNotSupported,
diff --git a/testing/ef_tests/src/cases/operations.rs b/testing/ef_tests/src/cases/operations.rs
index 350d52dcf2a..c72e4a2256d 100644
--- a/testing/ef_tests/src/cases/operations.rs
+++ b/testing/ef_tests/src/cases/operations.rs
@@ -131,12 +131,14 @@ impl<E: EthSpec> Operation<E> for Attestation<E> {
         initialize_progressive_balances_cache(state, spec)?;
         let mut ctxt = ConsensusContext::new(state.slot());
         if state.fork_name_unchecked().gloas_enabled() {
+            let parent_slot = Some(state.latest_execution_payload_bid()?.slot);
             gloas::process_attestation(
                 state,
                 self.to_ref(),
                 0,
-                &mut ctxt,
                 VerifySignatures::True,
+                parent_slot,
+                &mut ctxt,
                 spec,
             )
         } else if state.fork_name_unchecked().altair_enabled() {