4 files changed, 11 insertions, 20 deletions
diff --git a/packages/0x.js/src/index.ts b/packages/0x.js/src/index.ts
index 1b3e893ba..e529e2858 100644
--- a/packages/0x.js/src/index.ts
+++ b/packages/0x.js/src/index.ts
@@ -6,8 +6,6 @@ export {
     ECSignature,
     ZeroExError,
     EventCallback,
-    EventCallbackAsync,
-    EventCallbackSync,
     ExchangeContractErrs,
     ContractEvent,
     Token,
diff --git a/packages/0x.js/src/order_watcher/event_watcher.ts b/packages/0x.js/src/order_watcher/event_watcher.ts
index 81529a98c..c39431f6d 100644
--- a/packages/0x.js/src/order_watcher/event_watcher.ts
+++ b/packages/0x.js/src/order_watcher/event_watcher.ts
@@ -81,7 +81,7 @@ export class EventWatcher {
                 ...log,
             };
             if (!_.isUndefined(this._intervalIdIfExists)) {
-                await callback(logEvent);
+                callback(logEvent);
             }
         }
     }
diff --git a/packages/0x.js/src/order_watcher/order_state_watcher.ts b/packages/0x.js/src/order_watcher/order_state_watcher.ts
index bafd7a994..1b410dad1 100644
--- a/packages/0x.js/src/order_watcher/order_state_watcher.ts
+++ b/packages/0x.js/src/order_watcher/order_state_watcher.ts
@@ -52,7 +52,7 @@ interface OrderByOrderHash {
 export class OrderStateWatcher {
     private _orderByOrderHash: OrderByOrderHash = {};
     private _dependentOrderHashes: DependentOrderHashes = {};
-    private _callbackIfExistsAsync?: OnOrderStateChangeCallback;
+    private _callbackIfExists?: OnOrderStateChangeCallback;
     private _eventWatcher: EventWatcher;
     private _web3Wrapper: Web3Wrapper;
     private _abiDecoder: AbiDecoder;
@@ -106,22 +106,22 @@ export class OrderStateWatcher {
      */
     public subscribe(callback: OnOrderStateChangeCallback): void {
         assert.isFunction('callback', callback);
-        if (!_.isUndefined(this._callbackIfExistsAsync)) {
+        if (!_.isUndefined(this._callbackIfExists)) {
             throw new Error(ZeroExError.SubscriptionAlreadyPresent);
         }
-        this._callbackIfExistsAsync = callback;
+        this._callbackIfExists = callback;
         this._eventWatcher.subscribe(this._onEventWatcherCallbackAsync.bind(this));
     }
     /**
      * Ends an orderStateWatcher subscription.
      */
     public unsubscribe(): void {
-        if (_.isUndefined(this._callbackIfExistsAsync)) {
+        if (_.isUndefined(this._callbackIfExists)) {
             throw new Error(ZeroExError.SubscriptionNotFound);
         }
         this._balanceAndProxyAllowanceLazyStore.deleteAll();
         this._orderFilledCancelledLazyStore.deleteAll();
-        delete this._callbackIfExistsAsync;
+        delete this._callbackIfExists;
         this._eventWatcher.unsubscribe();
     }
     private async _onEventWatcherCallbackAsync(log: LogEvent): Promise<void> {
@@ -204,10 +204,10 @@ export class OrderStateWatcher {
             // Most of these calls will never reach the network because the data is fetched from stores
             // and only updated when cache is invalidated
             const orderState = await this._orderStateUtils.getOrderStateAsync(signedOrder);
-            if (_.isUndefined(this._callbackIfExistsAsync)) {
+            if (_.isUndefined(this._callbackIfExists)) {
                 break; // Unsubscribe was called
             }
-            await this._callbackIfExistsAsync(orderState);
+            this._callbackIfExists(orderState);
         }
     }
     private addToDependentOrderHashes(signedOrder: SignedOrder, orderHash: string) {
diff --git a/packages/0x.js/src/types.ts b/packages/0x.js/src/types.ts
index 71089f9a1..39e5fa9f2 100644
--- a/packages/0x.js/src/types.ts
+++ b/packages/0x.js/src/types.ts
@@ -42,13 +42,8 @@ export type OrderValues = [BigNumber, BigNumber, BigNumber,
 export type LogEvent = Web3.LogEntryEvent;
 export type DecodedLogEvent<ArgsType> = Web3.DecodedLogEntryEvent<ArgsType>;
 
-export type EventCallbackAsync<ArgsType> = (err: null|Error, log?: DecodedLogEvent<ArgsType>) => Promise<void>;
-export type EventCallbackSync<ArgsType> = (err: null|Error, log?: DecodedLogEvent<ArgsType>) => void;
-export type EventCallback<ArgsType> = EventCallbackSync<ArgsType>|EventCallbackAsync<ArgsType>;
-
-export type EventWatcherCallbackSync = (log: LogEvent) => void;
-export type EventWatcherCallbackAsync = (log: LogEvent) => Promise<void>;
-export type EventWatcherCallback = EventWatcherCallbackSync|EventWatcherCallbackAsync;
+export type EventCallback<ArgsType> = (err: null|Error, log?: DecodedLogEvent<ArgsType>) => void;
+export type EventWatcherCallback = (log: LogEvent) => void;
 
 export interface ExchangeContract extends Web3.ContractInstance {
     isValidSignature: {
@@ -507,9 +502,7 @@ export interface OrderStateInvalid {
 
 export type OrderState = OrderStateValid|OrderStateInvalid;
 
-export type OnOrderStateChangeCallbackSync = (orderState: OrderState) => void;
-export type OnOrderStateChangeCallbackAsync = (orderState: OrderState) => Promise<void>;
-export type OnOrderStateChangeCallback = OnOrderStateChangeCallbackAsync|OnOrderStateChangeCallbackSync;
+export type OnOrderStateChangeCallback = (orderState: OrderState) => void;
 
 export interface TransactionReceipt {
     blockHash: string;