Can I set just the maxFeePerGas?

I want to send OZ Defender Relay EIP-1559 transactions and only specify the maxFeePerGas. I want to leave it up to the Alchemy node to calculate the maxPriorityFeePerGas based on the baseFee and the maxFeePerGas. See the Alchemy docs about this.

:computer: Environment

I'm using the Defender Relayer to send transactions on behalf of users. We pay the gas fees for them and want to keep the fees bounded, so we have a preference to control the maxFeePerGas and care a bit less about how quickly a transaction makes it into a block.

We use these packages:

  • ethers@5.6.1
  • defender-relay-client@1.37.0
  • defender-base-client@1.37.0


I am trying to send transactions to the relayer using EIP-1559. I only want to set the maxFeePerGas and leave maxPriorityFeePerGas unset. I'm using the ethers.js Defender Relayer client because then I can easily wait on the transaction to be mined and use my standard ethers.js tooling that I've built elsewhere.

Looking at DefenderRelaySigner.sendTransaction, it seems that if I do not set both maxFeePerGas and maxPriorityFeePerGas then it looks like it won't even recognize that I specified the maxFeePerGas and it will recompute both the maxFeePerGas and the maxPriorityFeePerGas.

Is there any way to set just the maxFeePerGas? I prefer to use the Ethers.js Defender Relay client, but I can switch to another Defender Relay client.

:1234: Code to reproduce

import { Relayer, RelayerTransaction } from 'defender-relay-client'
import { ApiRelayerParams } from 'defender-relay-client/lib'
import { ForwarderV1__factory } from '@supercoolxyz/checkout-contracts'

const relayerParams: ApiRelayerParams = {
    apiKey: 'my key',
    apiSecret: 'my secret',

const forwarderAddress = '0xdeadbeef'

const provider = new DefenderRelayProvider(relayerParams)
const signer = new DefenderRelaySigner(relayerParams, provider)
const forwarder = ForwarderV1__factory.connect(forwarderAddress, signer)

const ethersMintReq = {
    // This is irrelevant. Use any typechain contract and its respective
    // arguments.
    // ...

const tx = await forwarder.forwardMint(ethersMintReq, {
  value: ethersMintReq.value,
  gasPrice: gasPrice,
  maxFeePerGas: maxFeePerGas,
  maxPriorityFeePerGas: maxPriorityFeePerGas,
  gasLimit: gasLimit
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