1 files changed, 7 insertions, 6 deletions
diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index 90b9a39d2..3f6eb0dab 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -7,11 +7,11 @@ import * as ExchangeArtifacts from '../artifacts/Exchange.json';
 import {ecSignatureSchema} from '../schemas/ec_signature_schema';
 
 export class ExchangeWrapper extends ContractWrapper {
-    private exchangeContractIfExists: ExchangeContract;
+    private exchangeContractIfExists?: ExchangeContract;
     constructor(web3Wrapper: Web3Wrapper) {
         super(web3Wrapper);
     }
-    public invalidateContractInstance() {
+    public invalidateContractInstance(): void {
         delete this.exchangeContractIfExists;
     }
     public async isValidSignatureAsync(dataHex: string, ecSignature: ECSignature,
@@ -23,9 +23,9 @@ export class ExchangeWrapper extends ContractWrapper {
         const senderAddressIfExists = await this.web3Wrapper.getSenderAddressIfExistsAsync();
         assert.assert(!_.isUndefined(senderAddressIfExists), ZeroExError.USER_HAS_NO_ASSOCIATED_ADDRESSES);
 
-        await this.instantiateExchangeContractIfDoesntExistAsync();
+        const exchangeContract = await this.getExchangeContractAsync();
 
-        const isValidSignature = await this.exchangeContractIfExists.isValidSignature.call(
+        const isValidSignature = await exchangeContract.isValidSignature.call(
             signerAddressHex,
             dataHex,
             ecSignature.v,
@@ -37,11 +37,12 @@ export class ExchangeWrapper extends ContractWrapper {
         );
         return isValidSignature;
     }
-    private async instantiateExchangeContractIfDoesntExistAsync() {
+    private async getExchangeContractAsync(): Promise<ExchangeContract> {
         if (!_.isUndefined(this.exchangeContractIfExists)) {
-            return;
+            return this.exchangeContractIfExists;
         }
         const contractInstance = await this.instantiateContractIfExistsAsync((ExchangeArtifacts as any));
         this.exchangeContractIfExists = contractInstance as ExchangeContract;
+        return this.exchangeContractIfExists;
     }
 }