diff --git a/crates/consensus/src/fork.rs b/crates/consensus/src/fork.rs
index b8dae27..68a4486 100644
--- a/crates/consensus/src/fork.rs
+++ b/crates/consensus/src/fork.rs
@@ -17,6 +17,11 @@ pub const GENESIS_SPEC: ForkSpec = ForkSpec {
     execution_payload_block_number_gindex: 0,
 };
 
+pub const ALTAIR_INDEX: usize = 0;
+pub const BELLATRIX_INDEX: usize = 1;
+pub const CAPELLA_INDEX: usize = 2;
+pub const DENEB_INDEX: usize = 3;
+
 /// Fork parameters for the beacon chain
 #[derive(Debug, Default, Clone, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
 pub struct ForkParameters {
@@ -63,19 +68,32 @@ impl ForkParameters {
     /// Compute the fork version for the given epoch
     pub fn compute_fork_version(&self, epoch: Epoch) -> Version {
         self.compute_fork(epoch)
-            .map(|f| f.version)
+            .map(|(_, f)| f.version.clone())
             .unwrap_or(self.genesis_version.clone())
     }
 
     /// Compute the fork spec for the given epoch
     pub fn compute_fork_spec(&self, epoch: Epoch) -> ForkSpec {
         self.compute_fork(epoch)
-            .map(|f| f.spec)
+            .map(|(_, f)| f.spec.clone())
             .unwrap_or(GENESIS_SPEC)
     }
 
-    fn compute_fork(&self, epoch: Epoch) -> Option<ForkParameter> {
-        self.forks.iter().rev().find(|f| epoch >= f.epoch).cloned()
+    /// Returns a boolean indicating whether the given epoch is after the fork
+    pub fn is_fork(&self, epoch: Epoch, fork_index: usize) -> bool {
+        if let Some((current, _)) = self.compute_fork(epoch) {
+            current >= fork_index
+        } else {
+            false
+        }
+    }
+
+    fn compute_fork(&self, epoch: Epoch) -> Option<(usize, &ForkParameter)> {
+        self.forks
+            .iter()
+            .enumerate()
+            .rev()
+            .find(|(_, f)| epoch >= f.epoch)
     }
 }
 
@@ -169,6 +187,13 @@ mod tests {
         assert_eq!(params.compute_fork_version(2.into()), Version([3, 0, 0, 1]));
         assert_eq!(params.compute_fork_version(3.into()), Version([4, 0, 0, 1]));
         assert_eq!(params.compute_fork_version(4.into()), Version([4, 0, 0, 1]));
+        assert!(params.is_fork(0.into(), ALTAIR_INDEX));
+        assert!(!params.is_fork(0.into(), BELLATRIX_INDEX));
+        assert!(params.is_fork(1.into(), ALTAIR_INDEX));
+        assert!(params.is_fork(1.into(), BELLATRIX_INDEX));
+        assert!(!params.is_fork(1.into(), CAPELLA_INDEX));
+        assert!(params.is_fork(3.into(), DENEB_INDEX));
+        assert!(params.is_fork(4.into(), DENEB_INDEX));
 
         let res = ForkParameters::new(
             Version([0, 0, 0, 1]),
diff --git a/crates/light-client-verifier/src/consensus.rs b/crates/light-client-verifier/src/consensus.rs
index 55f1204..6e1c342 100644
--- a/crates/light-client-verifier/src/consensus.rs
+++ b/crates/light-client-verifier/src/consensus.rs
@@ -12,7 +12,7 @@ use ethereum_consensus::compute::{
     compute_sync_committee_period_at_slot, hash_tree_root,
 };
 use ethereum_consensus::context::ChainContext;
-use ethereum_consensus::fork::ForkSpec;
+use ethereum_consensus::fork::{ForkSpec, BELLATRIX_INDEX};
 use ethereum_consensus::merkle::is_valid_normalized_merkle_branch;
 use ethereum_consensus::sync_protocol::SyncCommittee;
 use ethereum_consensus::types::H256;
@@ -249,6 +249,14 @@ pub fn validate_light_client_update<
     consensus_update: &CU,
 ) -> Result<(), Error> {
     consensus_update.validate_basic(ctx)?;
+    let finalized_epoch =
+        compute_epoch_at_slot(ctx, consensus_update.finalized_beacon_header().slot);
+    if !ctx
+        .fork_parameters()
+        .is_fork(finalized_epoch, BELLATRIX_INDEX)
+    {
+        return Err(Error::ForkNotSupported(finalized_epoch));
+    }
 
     let current_period = store.current_period(ctx);
     let signature_period =
diff --git a/crates/light-client-verifier/src/errors.rs b/crates/light-client-verifier/src/errors.rs
index 219f387..7fa9a6e 100644
--- a/crates/light-client-verifier/src/errors.rs
+++ b/crates/light-client-verifier/src/errors.rs
@@ -1,7 +1,7 @@
 use crate::internal_prelude::*;
 use displaydoc::Display;
 use ethereum_consensus::{
-    beacon::{BeaconBlockHeader, Root, Slot},
+    beacon::{BeaconBlockHeader, Epoch, Root, Slot},
     bls::PublicKey,
     errors::MerkleError,
     sync_protocol::SyncCommitteePeriod,
@@ -13,6 +13,8 @@ type BoxedTrieError = Box<TrieError<primitive_types::H256, rlp::DecoderError>>;
 
 #[derive(Debug, Display)]
 pub enum Error {
+    /// the light client does not support the fork corresponding to the finalized epoch: `epoch={0}`
+    ForkNotSupported(Epoch),
     /// unexpected signature period: `store={0} signature={1} reason={2}`
     UnexpectedSingaturePeriod(SyncCommitteePeriod, SyncCommitteePeriod, String),
     /// unexpected attested period: `store={0} attested={1} reason={2}`