2 files changed, 6 insertions, 4 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..68bdc2de7 100644
--- a/packages/contract-wrappers/src/contract_wrappers/erc20_proxy_wrapper.ts
+++ b/packages/contract-wrappers/src/contract_wrappers/erc20_proxy_wrapper.ts
@@ -3,6 +3,7 @@ import { ContractAbi } from 'ethereum-types';
 import * as _ from 'lodash';
 
 import { artifacts } from '../artifacts';
+import { AssetProxyId } from '../types';
 import { assert } from '../utils/assert';
 
 import { ContractWrapper } from './contract_wrapper';
@@ -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;
     }
     /**
diff --git a/packages/contract-wrappers/src/contract_wrappers/erc721_proxy_wrapper.ts b/packages/contract-wrappers/src/contract_wrappers/erc721_proxy_wrapper.ts
index 648c150df..e249f2f74 100644
--- a/packages/contract-wrappers/src/contract_wrappers/erc721_proxy_wrapper.ts
+++ b/packages/contract-wrappers/src/contract_wrappers/erc721_proxy_wrapper.ts
@@ -3,6 +3,7 @@ import { ContractAbi } from 'ethereum-types';
 import * as _ from 'lodash';
 
 import { artifacts } from '../artifacts';
+import { AssetProxyId } from '../types';
 import { assert } from '../utils/assert';
 
 import { ContractWrapper } from './contract_wrapper';
@@ -23,9 +24,9 @@ export class ERC721ProxyWrapper 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 ERC721ProxyContractInstance = await this._getERC721ProxyContractAsync();
-        const proxyId = await ERC721ProxyContractInstance.getProxyId.callAsync();
+        const proxyId = (await ERC721ProxyContractInstance.getProxyId.callAsync()) as AssetProxyId;
         return proxyId;
     }
     /**