diff --git a/contracts/.env.example.deployment b/contracts/.env.example.deployment
index 6d9a2a38..ac5cbcf7 100644
--- a/contracts/.env.example.deployment
+++ b/contracts/.env.example.deployment
@@ -9,4 +9,5 @@ export ADDRESS_KMS_SIGNER_3="0x2dac5193bE0AB0eD8871399E6Ae61EAe6cc8cAE1"
 export ADDRESS_COPROCESSOR_ACCOUNT="0xc9990FEfE0c27D31D0C2aa36196b085c0c4d456c"
 export IS_COPROCESSOR="true"
 export SEPOLIA_RPC_URL="https://sepolia.infura.io/v3/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
+export MAINNET_RPC_URL="https://mainnet.infura.io/v3/xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"
 export ETHERSCAN_API_KEY="XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX"
\ No newline at end of file
diff --git a/contracts/hardhat.config.ts b/contracts/hardhat.config.ts
index d0d9a7d2..4e0741f6 100644
--- a/contracts/hardhat.config.ts
+++ b/contracts/hardhat.config.ts
@@ -69,8 +69,12 @@ function getChainConfig(chain: keyof typeof chainIds): NetworkUserConfig {
       break;
     case 'sepolia':
       jsonRpcUrl = process.env.SEPOLIA_RPC_URL!;
+      break;
     case 'mainnet':
       jsonRpcUrl = process.env.MAINNET_RPC_URL!;
+      break;
+    default:
+      throw new Error(`unsupported chain: ${chain}`);
   }
   return {
     accounts: {