diff --git a/crypto_dev_signer/eth/transaction.py b/crypto_dev_signer/eth/transaction.py
index aefbccd..bba8cc5 100644
--- a/crypto_dev_signer/eth/transaction.py
+++ b/crypto_dev_signer/eth/transaction.py
@@ -152,7 +152,7 @@ class EIP155Transaction:
         if len(signature) < 65:
             raise ValueError('invalid signature length')
         if v == None:
-            v = signature[64]
+            v = chain_id_to_v(chain_id, signature)
         self.v = int_to_minbytes(v)
         self.r = signature[:32]
         self.s = signature[32:64]