diff --git a/README.md b/README.md
index 9853620..d1ba8f0 100644
--- a/README.md
+++ b/README.md
@@ -47,7 +47,7 @@ import {
 
 - connected: store value is true if a connection has been set up.
 - provider: store value is an Ethers.js Provider instance when connected.
-- chainId: store value is the current chainId when connected (always BigInt)
+- chainId: store value is the current chainId when connected (** always a BigInt **)
 - chainData: store value is the current blokchain CAIP-2 data (when connected), see below.
 - signer: store value is an Ethers.js Signer instance when connected.
 - signerAddress: store value is a shortcut to get `$signer.getAddress()` when connected.
diff --git a/src/stores.js b/src/stores.js
index 55d2c12..8efb41b 100644
--- a/src/stores.js
+++ b/src/stores.js
@@ -303,8 +303,9 @@ export const getChainStore = (name) => {
 
 export { chains as allChainsData };
 
+// chains.js only support number chainId
 export const getChainDataByChainId = (id) =>
-  (chains.filter((o) => o.chainId === id) || [{}])[0];
+(chains.filter((o) => o.chainId === Number(BigInt(id))) || [{}])[0];
 
 export const defaultEvmStores = makeEvmStores("default");