diff --git a/packages/contracts/contracts/optimistic-ethereum/OVM/accounts/OVM_ECDSAContractAccount.sol b/packages/contracts/contracts/optimistic-ethereum/OVM/accounts/OVM_ECDSAContractAccount.sol
index a7c2e2b1a457..c4654834ba8c 100644
--- a/packages/contracts/contracts/optimistic-ethereum/OVM/accounts/OVM_ECDSAContractAccount.sol
+++ b/packages/contracts/contracts/optimistic-ethereum/OVM/accounts/OVM_ECDSAContractAccount.sol
@@ -64,6 +64,12 @@ contract OVM_ECDSAContractAccount is iOVM_ECDSAContractAccount {
 
         Lib_OVMCodec.EIP155Transaction memory decodedTx = Lib_OVMCodec.decodeEIP155Transaction(_transaction, isEthSign);
 
+        // Need to make sure that the transaction chainId is correct.
+        Lib_SafeExecutionManagerWrapper.safeREQUIRE(
+            decodedTx.chainId == Lib_SafeExecutionManagerWrapper.safeCHAINID(),
+            "Transaction chainId does not match expected OVM chainId."
+        );
+
         // Need to make sure that the transaction nonce is right.
         Lib_SafeExecutionManagerWrapper.safeREQUIRE(
             decodedTx.nonce == Lib_SafeExecutionManagerWrapper.safeGETNONCE(),
diff --git a/packages/contracts/contracts/optimistic-ethereum/mockOVM/accounts/mockOVM_ECDSAContractAccount.sol b/packages/contracts/contracts/optimistic-ethereum/mockOVM/accounts/mockOVM_ECDSAContractAccount.sol
index d3a152da90ab..2ece58f9ea65 100644
--- a/packages/contracts/contracts/optimistic-ethereum/mockOVM/accounts/mockOVM_ECDSAContractAccount.sol
+++ b/packages/contracts/contracts/optimistic-ethereum/mockOVM/accounts/mockOVM_ECDSAContractAccount.sol
@@ -46,6 +46,12 @@ contract mockOVM_ECDSAContractAccount is iOVM_ECDSAContractAccount {
         bool isEthSign = _signatureType == Lib_OVMCodec.EOASignatureType.ETH_SIGNED_MESSAGE;
         Lib_OVMCodec.EIP155Transaction memory decodedTx = Lib_OVMCodec.decodeEIP155Transaction(_transaction, isEthSign);
 
+        // Need to make sure that the transaction chainId is correct.
+        Lib_SafeExecutionManagerWrapper.safeREQUIRE(
+            decodedTx.chainId == Lib_SafeExecutionManagerWrapper.safeCHAINID(),
+            "Transaction chainId does not match expected OVM chainId."
+        );
+
         // Need to make sure that the transaction nonce is right.
         Lib_SafeExecutionManagerWrapper.safeREQUIRE(
             decodedTx.nonce == Lib_SafeExecutionManagerWrapper.safeGETNONCE(),
diff --git a/packages/contracts/test/contracts/OVM/accounts/OVM_ECDSAContractAccount.spec.ts b/packages/contracts/test/contracts/OVM/accounts/OVM_ECDSAContractAccount.spec.ts
index d3d89df84c1b..8a5cb60c4bd2 100644
--- a/packages/contracts/test/contracts/OVM/accounts/OVM_ECDSAContractAccount.spec.ts
+++ b/packages/contracts/test/contracts/OVM/accounts/OVM_ECDSAContractAccount.spec.ts
@@ -200,5 +200,32 @@ describe('OVM_ECDSAContractAccount', () => {
         'Transaction nonce does not match the expected nonce.'
       )
     })
+
+    it(`should revert on incorrect chainId`, async () => {
+      const alteredChainIdTx = {
+        ...DEFAULT_EIP155_TX,
+        chainId : 421
+      }
+      const message = serializeNativeTransaction(alteredChainIdTx)
+      const sig = await signNativeTransaction(wallet, alteredChainIdTx)
+
+      await callPrecompile(
+        Helper_PrecompileCaller,
+        OVM_ECDSAContractAccount,
+        'execute',
+        [
+          message,
+          0, //isEthSignedMessage
+          `0x${sig.v}`, //v
+          `0x${sig.r}`, //r
+          `0x${sig.s}`, //s
+        ]
+      )
+      const ovmREVERT: any =
+        Mock__OVM_ExecutionManager.smocked.ovmREVERT.calls[0]
+      expect(ethers.utils.toUtf8String(ovmREVERT._data)).to.equal(
+        'Transaction chainId does not match expected OVM chainId.'
+      )
+    })
   })
 })
diff --git a/packages/contracts/test/helpers/codec/encoding.ts b/packages/contracts/test/helpers/codec/encoding.ts
index 4d3fe92f0df3..f2a10f1a6074 100644
--- a/packages/contracts/test/helpers/codec/encoding.ts
+++ b/packages/contracts/test/helpers/codec/encoding.ts
@@ -121,7 +121,7 @@ export const signNativeTransaction = async (
   let [v, r, s] = getSignedComponents(transactionSignature).map((component) => {
     return remove0x(component)
   })
-  v = '0' + (parseInt(v, 16) - 420 * 2 - 8 - 27)
+  v = '0' + (parseInt(v, 16) - transaction.chainId * 2 - 8 - 27)
   return {
     messageHash,
     v,