From 20449a0cb293649d9c301781dd89e7c26cc7a6b6 Mon Sep 17 00:00:00 2001
From: Leonid Logvinov <logvinov.leon@gmail.com>
Date: Mon, 20 Nov 2017 11:13:54 -0600
Subject: Throw when subscription is already removed

---
 packages/0x.js/src/order_watcher/expiration_watcher.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

(limited to 'packages')

diff --git a/packages/0x.js/src/order_watcher/expiration_watcher.ts b/packages/0x.js/src/order_watcher/expiration_watcher.ts
index 6d9556336..f9c6571db 100644
--- a/packages/0x.js/src/order_watcher/expiration_watcher.ts
+++ b/packages/0x.js/src/order_watcher/expiration_watcher.ts
@@ -35,7 +35,10 @@ export class ExpirationWatcher {
         );
     }
     public unsubscribe(): void {
-        intervalUtils.clearAsyncExcludingInterval(this.orderExpirationCheckingIntervalIdIfExists as NodeJS.Timer);
+        if (_.isUndefined(this.orderExpirationCheckingIntervalIdIfExists)) {
+            throw new Error(ZeroExError.SubscriptionNotFound);
+        }
+        intervalUtils.clearAsyncExcludingInterval(this.orderExpirationCheckingIntervalIdIfExists);
         delete this.callbackIfExists;
     }
     public addOrder(orderHash: string, expirationUnixTimestampSec: BigNumber): void {
-- 
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