1 files changed, 1 insertions, 1 deletions
diff --git a/packages/contracts/test/utils/simple_asset_balance_and_proxy_allowance_fetcher.ts b/packages/contracts/test/utils/simple_asset_balance_and_proxy_allowance_fetcher.ts
index a295a40c4..598ee6d29 100644
--- a/packages/contracts/test/utils/simple_asset_balance_and_proxy_allowance_fetcher.ts
+++ b/packages/contracts/test/utils/simple_asset_balance_and_proxy_allowance_fetcher.ts
@@ -4,7 +4,7 @@ import { BigNumber } from '@0xproject/utils';
 import { AssetWrapper } from './asset_wrapper';
 
 export class SimpleAssetBalanceAndProxyAllowanceFetcher implements AbstractBalanceAndProxyAllowanceFetcher {
-    private _assetWrapper: AssetWrapper;
+    private readonly _assetWrapper: AssetWrapper;
     constructor(assetWrapper: AssetWrapper) {
         this._assetWrapper = assetWrapper;
     }