1 files changed, 3 insertions, 2 deletions
diff --git a/packages/contract-wrappers/src/contract_wrappers/erc20_proxy_wrapper.ts b/packages/contract-wrappers/src/contract_wrappers/erc20_proxy_wrapper.ts
index 883d7c4d6..821d1a8a2 100644
--- a/packages/contract-wrappers/src/contract_wrappers/erc20_proxy_wrapper.ts
+++ b/packages/contract-wrappers/src/contract_wrappers/erc20_proxy_wrapper.ts
@@ -1,3 +1,4 @@
+import { AssetProxyId } from '@0xproject/types';
 import { Web3Wrapper } from '@0xproject/web3-wrapper';
 import { ContractAbi } from 'ethereum-types';
 import * as _ from 'lodash';
@@ -23,9 +24,9 @@ export class ERC20ProxyWrapper extends ContractWrapper {
      * Get the 4 bytes ID of this asset proxy
      * @return  Proxy id
      */
-    public async getProxyIdAsync(): Promise<string> {
+    public async getProxyIdAsync(): Promise<AssetProxyId> {
         const ERC20ProxyContractInstance = await this._getERC20ProxyContractAsync();
-        const proxyId = await ERC20ProxyContractInstance.getProxyId.callAsync();
+        const proxyId = (await ERC20ProxyContractInstance.getProxyId.callAsync()) as AssetProxyId;
         return proxyId;
     }
     /**