diff --git a/accounts/usbwallet/trezor.go b/accounts/usbwallet/trezor.go
index 30aa22dec3..42fb7bdc9c 100644
--- a/accounts/usbwallet/trezor.go
+++ b/accounts/usbwallet/trezor.go
@@ -251,8 +251,8 @@ func (w *trezorDriver) trezorSign(derivationPath []uint32, tx *types.Transaction
 	// Extract the Ethereum signature and do a sanity validation
 	if len(response.GetSignatureR()) == 0 || len(response.GetSignatureS()) == 0 {
 		return common.Address{}, nil, errors.New("reply lacks signature")
-	} else if response.GetSignatureV() == 0 && int(chainID.Int64()) < 2147483630 {
-		// for chainId >= 2147483630, Trezor returns signature bit only
+	} else if response.GetSignatureV() == 0 && int(chainID.Int64()) < uint32 {
+		// for chainId >= (MaxUint32-36)/2, Trezor returns signature bit only
 		// https://github.com/trezor/trezor-mcu/pull/399
 		return common.Address{}, nil, errors.New("reply lacks signature")
 	}
@@ -265,6 +265,8 @@ func (w *trezorDriver) trezorSign(derivationPath []uint32, tx *types.Transaction
 	} else {
 		// Trezor backend does not support typed transactions yet.
 		signer = types.NewEIP155Signer(chainID)
+		// if chainId is above (MaxUint32 - 36) / 2 then the final v values is returned
+		// directly. Otherwise, the returned value is 35 + chainid * 2.
 		if signature[64] > 1 {
 			signature[64] -= byte(chainID.Uint64()*2 + 35)
 		}