diff --git a/src/processor-utils.js b/src/processor-utils.js
index 08c69882..0b5eb699 100644
--- a/src/processor-utils.js
+++ b/src/processor-utils.js
@@ -23,8 +23,10 @@ function unarrayifyInteger(data, offset, length) {
 }
 
 /**
- * Convert a custom rawTx  [rlp(nonce, gasprice, gaslimit, to, value, data, chainId, 0, 0)|r|s|v|effectivePercentage]
- * to a standard raw tx [rlp(nonce, gasprice, gaslimit, to, value, data, r, s, v)]
+ * Convert a custom rawTx:
+ *   - preEIP155: [rlp(nonce, gasprice, gaslimit, to, value, data)|r|s|v|effectivePercentage]
+ *   - Legacy: [rlp(nonce, gasprice, gaslimit, to, value, data, chainId, 0, 0)|r|s|v|effectivePercentage]
+ * to a standard raw ethereum tx: [rlp(nonce, gasprice, gaslimit, to, value, data, r, s, v)]
  * @param {String} customRawTx -  Custom raw transaction
  * @returns {String} - Standar raw transaction
  */
@@ -104,27 +106,53 @@ function addressToHexStringRlp(address) {
 }
 
 /**
- * Convert a standar rawTx of ethereum [rlp(nonce,gasprice,gaslimit,to,value,data,r,s,v)]
- * to our custom raw tx [rlp(nonce,gasprice,gaslimit,to,value,data,0,0)|r|s|v|effectivePercentage]
+ * Convert a standard rawTx of ethereum [rlp(nonce,gasprice,gaslimit,to,value,data,r,s,v)]
+ * to our custom raw tx:
+ *   - preEIP155: [rlp(nonce,gasprice,gaslimit,to,value,data)|r|s|v|effectivePercentage]
+ *   - Legacy: [rlp(nonce,gasprice,gaslimit,to,value,data,chainId,0,0)|r|s|v|effectivePercentage]
  * @param {String} rawTx - Standar raw transaction
  * @returns {String} - Custom raw transaction
  */
 function rawTxToCustomRawTx(rawTx, effectivePercentage) {
     const tx = ethers.utils.parseTransaction(rawTx);
-    const signData = ethers.utils.RLP.encode([
-        toHexStringRlp(tx.nonce),
-        toHexStringRlp(tx.gasPrice),
-        toHexStringRlp(tx.gasLimit),
-        addressToHexStringRlp(tx.to || '0x'),
-        toHexStringRlp(tx.value),
-        toHexStringRlp(tx.data),
-        toHexStringRlp(tx.chainId),
-        '0x',
-        '0x',
-    ]);
-    const r = tx.r.slice(2);
-    const s = tx.s.slice(2);
-    const v = (tx.v - tx.chainId * 2 - 35 + 27).toString(16).padStart(2, '0'); // 1 byte
+
+    let signData;
+    let r;
+    let s;
+    let v;
+
+    // check preEIP155
+    if (tx.chainId === 0 && (tx.v === 27 || tx.v === 28)) {
+        signData = ethers.utils.RLP.encode([
+            toHexStringRlp(tx.nonce),
+            toHexStringRlp(tx.gasPrice),
+            toHexStringRlp(tx.gasLimit),
+            addressToHexStringRlp(tx.to || '0x'),
+            toHexStringRlp(tx.value),
+            toHexStringRlp(tx.data),
+        ]);
+
+        r = tx.r.slice(2);
+        s = tx.s.slice(2);
+        v = tx.v.toString(16).padStart(2, '0'); // 1 byte
+    } else {
+        signData = ethers.utils.RLP.encode([
+            toHexStringRlp(tx.nonce),
+            toHexStringRlp(tx.gasPrice),
+            toHexStringRlp(tx.gasLimit),
+            addressToHexStringRlp(tx.to || '0x'),
+            toHexStringRlp(tx.value),
+            toHexStringRlp(tx.data),
+            toHexStringRlp(tx.chainId),
+            '0x',
+            '0x',
+        ]);
+
+        r = tx.r.slice(2);
+        s = tx.s.slice(2);
+        v = (tx.v - tx.chainId * 2 - 35 + 27).toString(16).padStart(2, '0'); // 1 byte
+    }
+
     if (typeof effectivePercentage === 'undefined') {
         effectivePercentage = 'ff';
     }
diff --git a/test/helpers/test-vectors/block-info/block-info-batches.json b/test/helpers/test-vectors/block-info/block-info-batches.json
index ed885fb1..98ae603a 100644
--- a/test/helpers/test-vectors/block-info/block-info-batches.json
+++ b/test/helpers/test-vectors/block-info/block-info-batches.json
@@ -588,7 +588,53 @@
             "indexL1InfoTree": 0,
             "reason": "",
             "customRawTx": "0x0b0000000100000000"
+          }
+        ],
+        "expectedNewRoot": "0x74a2715780b47d57d1a82a10d884ad6b86768567986f44f3fdc609622faec7c7",
+        "expectedNewLeafs": {
+          "0x000000000000000000000000000000005ca1ab1e": {
+            "balance": "0",
+            "nonce": "0",
+            "storage": {
+              "0x0000000000000000000000000000000000000000000000000000000000000000": "0x01",
+              "0x0000000000000000000000000000000000000000000000000000000000000002": "0x01",
+              "0xa6eef7e35abe7026729641147f7915573c7e97b47efa546f5f6e3230263bcb49": "0xf5c30bbb2b8a1bdd2b881cc575b2acbd13578c7cd64250fe8b6770fa95f915b3"
+            }
+          },
+          "0x0000000000000000000000000000000000000000": {
+            "balance": "0",
+            "nonce": "0"
+          },
+          "0xae4bb80be56b819606589de61d5ec3b522eeb032": {
+            "balance": "0",
+            "nonce": "0"
+          },
+          "0x617b3a3528f9cdd6630fd3301b9c8911f7bf063d": {
+            "balance": "100000000000000000000",
+            "nonce": "1",
+            "pvtKey": "0x28b2b0318721be8c8339199172cd7cc8f5e273800a35616ec893083a4b32c02e"
+          },
+          "0x1275fbb540c8efc58b812ba83b0d0b8b9917ae98": {
+            "balance": "0",
+            "nonce": "1",
+            "storage": {}
           },
+          "0x4d5cf5032b2a844602278b01199ed191a86c93ff": {
+            "pvtKey": "0x4d27a600dce8c29b7bd080e29a26972377dbb04d7a27d919adbb602bf13cfd23",
+            "balance": "200000000000000000000",
+            "nonce": "0"
+          }
+        },
+        "batchL2Data": "0x0b0000000100000000",
+        "l1InfoRoot": "0x090bcaf734c4f06c93954a827b45a6e8c67b8e0fd1e0a35a1c5982d6961828f9",
+        "newLocalExitRoot": "0x0000000000000000000000000000000000000000000000000000000000000000",
+        "batchHashData": "0x7b643f52ec2fd0b23082647c621499c4a0ca105461bdf961d7c016ee411973ba",
+        "timestampLimit": 1944498040,
+        "skipFirstChangeL2Block": false,
+        "skipWriteBlockInfoRoot": true
+      },
+      {
+        "txs": [
           {
             "from": "0x4d5Cf5032B2a844602278b01199ED191A86c93ff",
             "to": "0x1275fbb540c8efc58b812ba83b0d0b8b9917ae98",
@@ -641,12 +687,12 @@
             }
           }
         },
-        "batchL2Data": "0x0b0000000100000000ea80843b9aca00830186a0941275fbb540c8efc58b812ba83b0d0b8b9917ae988084188ec3568203e880800a62ce9876e027f7a954f96c485c63c9bf043bd1fe1012c5634cf959bf7743190a601eedbcfef58146bdda9845fea5d9356b09d667010d557c73f83353a119a61cff",
+        "batchL2Data": "0xea80843b9aca00830186a0941275fbb540c8efc58b812ba83b0d0b8b9917ae988084188ec3568203e880800a62ce9876e027f7a954f96c485c63c9bf043bd1fe1012c5634cf959bf7743190a601eedbcfef58146bdda9845fea5d9356b09d667010d557c73f83353a119a61cff",
         "l1InfoRoot": "0x090bcaf734c4f06c93954a827b45a6e8c67b8e0fd1e0a35a1c5982d6961828f9",
         "newLocalExitRoot": "0x0000000000000000000000000000000000000000000000000000000000000000",
-        "batchHashData": "0xd4af160abcacc3dfdedd6047930d4fe4cc24fb5aacb6342111c141e529ca0952",
+        "batchHashData": "0x678a508ff7895915da8bf0f0f2c1a7f16bfb873d853f4c5e20fb15730d5d6ad2",
         "timestampLimit": 1944498040,
-        "skipFirstChangeL2Block": false,
+        "skipFirstChangeL2Block": true,
         "skipWriteBlockInfoRoot": true
       },
       {
diff --git a/test/processor-utils.test.js b/test/processor-utils.test.js
index 9da2eec4..699619fd 100644
--- a/test/processor-utils.test.js
+++ b/test/processor-utils.test.js
@@ -219,4 +219,27 @@ describe('Processor utils', () => {
             }
         }
     });
+
+    it('rawTxToCustomRawTx & customRawTxToRawTx', async () => {
+        // preEIP155 & Legacy Etheruem transactions
+        const testVector = [
+            {
+                customRawTx: '0xea80843b9aca00830186a0941275fbb540c8efc58b812ba83b0d0b8b9917ae98808464fbb77c8203e88080fb5252bea10b359c0c5998b4d8185bb02e3503112e930f578dfb94f8e929cf4b2501bfdc00a066681e3b5ee9427ca97dfb8de68d570d8c36d5e3f8e9d6acfe4b1b01',
+            },
+            {
+                customRawTx: '0xe580843b9aca00830186a0941275fbb540c8efc58b812ba83b0d0b8b9917ae98808464fbb77c6b39bdc5f8e458aba689f2a1ff8c543a94e4817bda40f3fe34080c4ab26c1e3c2fc2cda93bc32f0a79940501fd505dcf48d94abfde932ebf1417f502cb0d9de81b10',
+            },
+        ];
+
+        for (let i = 0; i < testVector.length; i++) {
+            const { customRawTx } = testVector[i];
+            const effectivePercentage = customRawTx.slice(-2);
+
+            // compute rawTx
+            const rawTx = await processorUtils.customRawTxToRawTx(customRawTx);
+            // recompute customRawTx
+            const computedCustomRawTx = processorUtils.rawTxToCustomRawTx(rawTx, effectivePercentage);
+            expect(computedCustomRawTx).to.be.equal(customRawTx);
+        }
+    });
 });