diff --git a/src/0x.ts b/src/0x.ts
index 36ebb8ec2d..904765633b 100644
--- a/src/0x.ts
+++ b/src/0x.ts
@@ -164,9 +164,6 @@ export class ZeroEx {
      */
     constructor(provider: Web3Provider, gasPrice?: BigNumber.BigNumber) {
         this._web3Wrapper = new Web3Wrapper(provider);
-        if (_.isUndefined(gasPrice)) {
-            gasPrice = this._web3Wrapper.toWei(new BigNumber(21), 'gwei');
-        }
         this.token = new TokenWrapper(this._web3Wrapper, gasPrice);
         this.proxy = new TokenTransferProxyWrapper(this._web3Wrapper, gasPrice);
         this.exchange = new ExchangeWrapper(this._web3Wrapper, this.token, gasPrice);
diff --git a/src/contract_wrappers/contract_wrapper.ts b/src/contract_wrappers/contract_wrapper.ts
index 015ed275aa..28df82cee7 100644
--- a/src/contract_wrappers/contract_wrapper.ts
+++ b/src/contract_wrappers/contract_wrapper.ts
@@ -6,8 +6,8 @@ import {utils} from '../utils/utils';
 
 export class ContractWrapper {
     protected _web3Wrapper: Web3Wrapper;
-    private _gasPrice: BigNumber.BigNumber;
-    constructor(web3Wrapper: Web3Wrapper, gasPrice: BigNumber.BigNumber) {
+    private _gasPrice?: BigNumber.BigNumber;
+    constructor(web3Wrapper: Web3Wrapper, gasPrice?: BigNumber.BigNumber) {
         this._web3Wrapper = web3Wrapper;
         this._gasPrice = gasPrice;
     }
diff --git a/src/contract_wrappers/ether_token_wrapper.ts b/src/contract_wrappers/ether_token_wrapper.ts
index eae84feec4..3c282510f2 100644
--- a/src/contract_wrappers/ether_token_wrapper.ts
+++ b/src/contract_wrappers/ether_token_wrapper.ts
@@ -13,7 +13,7 @@ import * as EtherTokenArtifacts from '../artifacts/EtherToken.json';
 export class EtherTokenWrapper extends ContractWrapper {
     private _etherTokenContractIfExists?: EtherTokenContract;
     private _tokenWrapper: TokenWrapper;
-    constructor(web3Wrapper: Web3Wrapper, tokenWrapper: TokenWrapper, gasPrice: BigNumber.BigNumber) {
+    constructor(web3Wrapper: Web3Wrapper, tokenWrapper: TokenWrapper, gasPrice?: BigNumber.BigNumber) {
         super(web3Wrapper, gasPrice);
         this._tokenWrapper = tokenWrapper;
     }
diff --git a/src/contract_wrappers/exchange_wrapper.ts b/src/contract_wrappers/exchange_wrapper.ts
index 8ae51da430..d09df236bd 100644
--- a/src/contract_wrappers/exchange_wrapper.ts
+++ b/src/contract_wrappers/exchange_wrapper.ts
@@ -73,7 +73,7 @@ export class ExchangeWrapper extends ContractWrapper {
         ];
         return [orderAddresses, orderValues];
     }
-    constructor(web3Wrapper: Web3Wrapper, tokenWrapper: TokenWrapper, gasPrice: BigNumber.BigNumber) {
+    constructor(web3Wrapper: Web3Wrapper, tokenWrapper: TokenWrapper, gasPrice?: BigNumber.BigNumber) {
         super(web3Wrapper, gasPrice);
         this._tokenWrapper = tokenWrapper;
         this._orderValidationUtils = new OrderValidationUtils(tokenWrapper, this);
diff --git a/src/contract_wrappers/token_registry_wrapper.ts b/src/contract_wrappers/token_registry_wrapper.ts
index 5469b4a950..822e69460c 100644
--- a/src/contract_wrappers/token_registry_wrapper.ts
+++ b/src/contract_wrappers/token_registry_wrapper.ts
@@ -11,7 +11,7 @@ import * as TokenRegistryArtifacts from '../artifacts/TokenRegistry.json';
  */
 export class TokenRegistryWrapper extends ContractWrapper {
     private _tokenRegistryContractIfExists?: TokenRegistryContract;
-    constructor(web3Wrapper: Web3Wrapper, gasPrice: BigNumber.BigNumber) {
+    constructor(web3Wrapper: Web3Wrapper, gasPrice?: BigNumber.BigNumber) {
         super(web3Wrapper, gasPrice);
     }
     /**
diff --git a/src/contract_wrappers/token_wrapper.ts b/src/contract_wrappers/token_wrapper.ts
index 24f56a24a5..f7070f1f48 100644
--- a/src/contract_wrappers/token_wrapper.ts
+++ b/src/contract_wrappers/token_wrapper.ts
@@ -31,7 +31,7 @@ export class TokenWrapper extends ContractWrapper {
     public UNLIMITED_ALLOWANCE_IN_BASE_UNITS = constants.UNLIMITED_ALLOWANCE_IN_BASE_UNITS;
     private _tokenContractsByAddress: {[address: string]: TokenContract};
     private _tokenLogEventEmitters: ContractEventEmitter[];
-    constructor(web3Wrapper: Web3Wrapper, gasPrice: BigNumber.BigNumber) {
+    constructor(web3Wrapper: Web3Wrapper, gasPrice?: BigNumber.BigNumber) {
         super(web3Wrapper, gasPrice);
         this._tokenContractsByAddress = {};
         this._tokenLogEventEmitters = [];