diff --git a/Cargo.lock b/Cargo.lock
index b18ccfcde8..134ebd6ac0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1928,6 +1928,7 @@ name = "fc-mapping-sync"
 version = "2.0.0-dev"
 dependencies = [
  "fc-db",
+ "fc-storage",
  "fp-consensus",
  "fp-rpc",
  "futures",
diff --git a/client/mapping-sync/Cargo.toml b/client/mapping-sync/Cargo.toml
index 80957cd616..5ca2705103 100644
--- a/client/mapping-sync/Cargo.toml
+++ b/client/mapping-sync/Cargo.toml
@@ -21,5 +21,6 @@ sp-blockchain = { workspace = true }
 sp-runtime = { workspace = true }
 # Frontier
 fc-db = { workspace = true }
+fc-storage = { workspace = true }
 fp-consensus = { workspace = true, features = ["default"] }
 fp-rpc = { workspace = true, features = ["default"] }
diff --git a/client/mapping-sync/src/lib.rs b/client/mapping-sync/src/lib.rs
index f84397b327..70d5794968 100644
--- a/client/mapping-sync/src/lib.rs
+++ b/client/mapping-sync/src/lib.rs
@@ -22,8 +22,10 @@ mod worker;
 
 pub use worker::{MappingSyncWorker, SyncStrategy};
 
+use std::sync::Arc;
+
 // Substrate
-use sc_client_api::backend::Backend;
+use sc_client_api::backend::{Backend, StorageProvider};
 use sp_api::{ApiExt, ProvideRuntimeApi};
 use sp_blockchain::{Backend as _, HeaderBackend};
 use sp_runtime::{
@@ -31,31 +33,78 @@ use sp_runtime::{
 	traits::{Block as BlockT, Header as HeaderT, Zero},
 };
 // Frontier
-use fp_consensus::FindLogError;
+use fc_storage::OverrideHandle;
+use fp_consensus::{FindLogError, Hashes, Log, PostLog, PreLog};
 use fp_rpc::EthereumRuntimeRPCApi;
 
-pub fn sync_block<Block: BlockT>(
+pub fn sync_block<Block: BlockT, C, BE>(
+	client: &C,
+	overrides: Arc<OverrideHandle<Block>>,
 	backend: &fc_db::Backend<Block>,
 	header: &Block::Header,
-) -> Result<(), String> {
+) -> Result<(), String>
+where
+	C: StorageProvider<Block, BE> + HeaderBackend<Block>,
+	BE: Backend<Block>,
+{
+	let substrate_block_hash = header.hash();
 	match fp_consensus::find_log(header.digest()) {
 		Ok(log) => {
-			let post_hashes = log.into_hashes();
-
-			let mapping_commitment = fc_db::MappingCommitment {
-				block_hash: header.hash(),
-				ethereum_block_hash: post_hashes.block_hash,
-				ethereum_transaction_hashes: post_hashes.transaction_hashes,
+			let gen_from_hashes = |hashes: Hashes| -> fc_db::MappingCommitment<Block> {
+				fc_db::MappingCommitment {
+					block_hash: substrate_block_hash,
+					ethereum_block_hash: hashes.block_hash,
+					ethereum_transaction_hashes: hashes.transaction_hashes,
+				}
+			};
+			let gen_from_block = |block| -> fc_db::MappingCommitment<Block> {
+				let hashes = Hashes::from_block(block);
+				gen_from_hashes(hashes)
 			};
-			backend.mapping().write_hashes(mapping_commitment)?;
-
-			Ok(())
-		}
-		Err(FindLogError::NotFound) => {
-			backend.mapping().write_none(header.hash())?;
 
-			Ok(())
+			match log {
+				Log::Pre(PreLog::Block(block)) => {
+					let mapping_commitment = gen_from_block(block);
+					backend.mapping().write_hashes(mapping_commitment)
+				}
+				Log::Post(post_log) => match post_log {
+					PostLog::Hashes(hashes) => {
+						let mapping_commitment = gen_from_hashes(hashes);
+						backend.mapping().write_hashes(mapping_commitment)
+					}
+					PostLog::Block(block) => {
+						let mapping_commitment = gen_from_block(block);
+						backend.mapping().write_hashes(mapping_commitment)
+					}
+					PostLog::BlockHash(expect_eth_block_hash) => {
+						let schema =
+							fc_storage::onchain_storage_schema(client, substrate_block_hash);
+						let ethereum_block = overrides
+							.schemas
+							.get(&schema)
+							.unwrap_or(&overrides.fallback)
+							.current_block(substrate_block_hash);
+						match ethereum_block {
+							Some(block) => {
+								let got_eth_block_hash = block.header.hash();
+								if got_eth_block_hash != expect_eth_block_hash {
+									Err(format!(
+										"Ethereum block hash mismatch: \
+										frontier consensus digest ({expect_eth_block_hash:?}), \
+										db state ({got_eth_block_hash:?})"
+									))
+								} else {
+									let mapping_commitment = gen_from_block(block);
+									backend.mapping().write_hashes(mapping_commitment)
+								}
+							}
+							None => backend.mapping().write_none(substrate_block_hash),
+						}
+					}
+				},
+			}
 		}
+		Err(FindLogError::NotFound) => backend.mapping().write_none(substrate_block_hash),
 		Err(FindLogError::MultipleLogs) => Err("Multiple logs found".to_string()),
 	}
 }
@@ -109,6 +158,7 @@ where
 pub fn sync_one_block<Block: BlockT, C, BE>(
 	client: &C,
 	substrate_backend: &BE,
+	overrides: Arc<OverrideHandle<Block>>,
 	frontier_backend: &fc_db::Backend<Block>,
 	sync_from: <Block::Header as HeaderT>::Number,
 	strategy: SyncStrategy,
@@ -116,7 +166,7 @@ pub fn sync_one_block<Block: BlockT, C, BE>(
 where
 	C: ProvideRuntimeApi<Block>,
 	C::Api: EthereumRuntimeRPCApi<Block>,
-	C: HeaderBackend<Block>,
+	C: HeaderBackend<Block> + StorageProvider<Block, BE>,
 	BE: Backend<Block>,
 {
 	let mut current_syncing_tips = frontier_backend.meta().current_syncing_tips()?;
@@ -167,7 +217,7 @@ where
 		{
 			return Ok(false);
 		}
-		sync_block(frontier_backend, &operating_header)?;
+		sync_block(client, overrides, frontier_backend, &operating_header)?;
 
 		current_syncing_tips.push(*operating_header.parent_hash());
 		frontier_backend
@@ -180,6 +230,7 @@ where
 pub fn sync_blocks<Block: BlockT, C, BE>(
 	client: &C,
 	substrate_backend: &BE,
+	overrides: Arc<OverrideHandle<Block>>,
 	frontier_backend: &fc_db::Backend<Block>,
 	limit: usize,
 	sync_from: <Block::Header as HeaderT>::Number,
@@ -188,7 +239,7 @@ pub fn sync_blocks<Block: BlockT, C, BE>(
 where
 	C: ProvideRuntimeApi<Block>,
 	C::Api: EthereumRuntimeRPCApi<Block>,
-	C: HeaderBackend<Block>,
+	C: HeaderBackend<Block> + StorageProvider<Block, BE>,
 	BE: Backend<Block>,
 {
 	let mut synced_any = false;
@@ -198,6 +249,7 @@ where
 			|| sync_one_block(
 				client,
 				substrate_backend,
+				overrides.clone(),
 				frontier_backend,
 				sync_from,
 				strategy,
diff --git a/client/mapping-sync/src/worker.rs b/client/mapping-sync/src/worker.rs
index 6fbe25d705..06702cbe1a 100644
--- a/client/mapping-sync/src/worker.rs
+++ b/client/mapping-sync/src/worker.rs
@@ -25,11 +25,15 @@ use futures::{
 use futures_timer::Delay;
 use log::debug;
 // Substrate
-use sc_client_api::{backend::Backend, client::ImportNotifications};
+use sc_client_api::{
+	backend::{Backend, StorageProvider},
+	client::ImportNotifications,
+};
 use sp_api::ProvideRuntimeApi;
 use sp_blockchain::HeaderBackend;
 use sp_runtime::traits::{Block as BlockT, Header as HeaderT};
 // Frontier
+use fc_storage::OverrideHandle;
 use fp_rpc::EthereumRuntimeRPCApi;
 
 #[derive(Copy, Clone, Eq, PartialEq)]
@@ -45,6 +49,7 @@ pub struct MappingSyncWorker<Block: BlockT, C, BE> {
 
 	client: Arc<C>,
 	substrate_backend: Arc<BE>,
+	overrides: Arc<OverrideHandle<Block>>,
 	frontier_backend: Arc<fc_db::Backend<Block>>,
 
 	have_next: bool,
@@ -61,6 +66,7 @@ impl<Block: BlockT, C, BE> MappingSyncWorker<Block, C, BE> {
 		timeout: Duration,
 		client: Arc<C>,
 		substrate_backend: Arc<BE>,
+		overrides: Arc<OverrideHandle<Block>>,
 		frontier_backend: Arc<fc_db::Backend<Block>>,
 		retry_times: usize,
 		sync_from: <Block::Header as HeaderT>::Number,
@@ -73,6 +79,7 @@ impl<Block: BlockT, C, BE> MappingSyncWorker<Block, C, BE> {
 
 			client,
 			substrate_backend,
+			overrides,
 			frontier_backend,
 
 			have_next: true,
@@ -87,7 +94,7 @@ impl<Block: BlockT, C, BE> Stream for MappingSyncWorker<Block, C, BE>
 where
 	C: ProvideRuntimeApi<Block>,
 	C::Api: EthereumRuntimeRPCApi<Block>,
-	C: HeaderBackend<Block>,
+	C: HeaderBackend<Block> + StorageProvider<Block, BE>,
 	BE: Backend<Block>,
 {
 	type Item = ();
@@ -125,6 +132,7 @@ where
 			match crate::sync_blocks(
 				self.client.as_ref(),
 				self.substrate_backend.as_ref(),
+				self.overrides.clone(),
 				self.frontier_backend.as_ref(),
 				self.retry_times,
 				self.sync_from,
diff --git a/primitives/consensus/src/lib.rs b/primitives/consensus/src/lib.rs
index f66b782bad..370d3a40c6 100644
--- a/primitives/consensus/src/lib.rs
+++ b/primitives/consensus/src/lib.rs
@@ -34,16 +34,6 @@ pub enum Log {
 	Post(PostLog),
 }
 
-impl Log {
-	pub fn into_hashes(self) -> Hashes {
-		match self {
-			Log::Post(PostLog::Hashes(post_hashes)) => post_hashes,
-			Log::Post(PostLog::Block(block)) => Hashes::from_block(block),
-			Log::Pre(PreLog::Block(block)) => Hashes::from_block(block),
-		}
-	}
-}
-
 #[derive(Decode, Encode, Clone, PartialEq, Eq)]
 pub enum PreLog {
 	#[codec(index = 3)]
@@ -52,10 +42,15 @@ pub enum PreLog {
 
 #[derive(Decode, Encode, Clone, PartialEq, Eq)]
 pub enum PostLog {
+	/// Ethereum block hash and txn hashes.
 	#[codec(index = 1)]
 	Hashes(Hashes),
+	/// Ethereum block.
 	#[codec(index = 2)]
 	Block(ethereum::BlockV2),
+	/// Ethereum block hash.
+	#[codec(index = 3)]
+	BlockHash(H256),
 }
 
 #[derive(Decode, Encode, Clone, PartialEq, Eq)]
@@ -68,17 +63,13 @@ pub struct Hashes {
 
 impl Hashes {
 	pub fn from_block(block: ethereum::BlockV2) -> Self {
-		let mut transaction_hashes = Vec::new();
-
-		for t in &block.transactions {
-			transaction_hashes.push(t.hash());
-		}
-
-		let block_hash = block.header.hash();
-
 		Hashes {
-			transaction_hashes,
-			block_hash,
+			block_hash: block.header.hash(),
+			transaction_hashes: block
+				.transactions
+				.into_iter()
+				.map(|txn| txn.hash())
+				.collect(),
 		}
 	}
 }
diff --git a/template/node/src/eth.rs b/template/node/src/eth.rs
index 4bae5d9099..cf0b6c56b6 100644
--- a/template/node/src/eth.rs
+++ b/template/node/src/eth.rs
@@ -128,6 +128,7 @@ pub fn spawn_frontier_tasks<RuntimeApi, Executor>(
 			Duration::new(6, 0),
 			client.clone(),
 			backend,
+			overrides.clone(),
 			frontier_backend,
 			3,
 			0,