diff --git a/web3_proxy/src/app/mod.rs b/web3_proxy/src/app/mod.rs
index 0ccb7e67..528d4376 100644
--- a/web3_proxy/src/app/mod.rs
+++ b/web3_proxy/src/app/mod.rs
@@ -804,7 +804,7 @@ impl Web3ProxyApp {
                 }
             }
             "eth_chainId" => {
-                json!(self.config.chain_id)
+                json!(U64::from(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)