diff --git a/web3_proxy/src/app/mod.rs b/web3_proxy/src/app/mod.rs
index eda5aebc..0ccb7e67 100644
--- a/web3_proxy/src/app/mod.rs
+++ b/web3_proxy/src/app/mod.rs
@@ -803,6 +803,9 @@ impl Web3ProxyApp {
                     }
                 }
             }
+            "eth_chainId" => {
+                json!(self.config.chain_id)
+            }
             // TODO: eth_callBundle (https://docs.flashbots.net/flashbots-auction/searchers/advanced/rpc-endpoint#eth_callbundle)
             // TODO: eth_cancelPrivateTransaction (https://docs.flashbots.net/flashbots-auction/searchers/advanced/rpc-endpoint#eth_cancelprivatetransaction, but maybe just reject)
             // TODO: eth_sendPrivateTransaction (https://docs.flashbots.net/flashbots-auction/searchers/advanced/rpc-endpoint#eth_sendprivatetransaction)