title: Error HH604: Error running JSON-RPC server: Unknown transaction type 106
body: <p>I try to fork mainnet by running <code>yarn hardhat node</code> and I get that error.
  <code>Error HH604: Error running JSON-RPC server: Unknown transaction type 106</code></p>
  <p>My <strong>hardhat.config.js</strong> file has forking settings.</p>
  <pre><code>require(&quot;@nomiclabs/hardhat-ethers&quot;);
  require(&quot;dotenv&quot;).config();
  
  /** @type import('hardhat/config').HardhatUserConfig */
  module.exports = {
    solidity: &quot;0.8.17&quot;,
    defaultNetwork: &quot;hardhat&quot;,
    networks: {
      hardhat: {
        chainId: 31337,
        forking: {
          url: process.env.ARBITRUM_RPC_URL,
        },
      },
    },
  };
  </code></pre>
  <p>I have tried edit my <code>package.json</code> based on <a href="https://stackoverflow.com/a/69748147/18073055">this solution.</a> and run <code>yarn start</code>.</p>
  <p>After that, I get <code>--openssl-legacy-provider is not allowed in NODE_OPTIONS</code> error. I have tried to downgrade Node to <code>v16</code> but I get still the same error.</p>