diff --git a/lib/NetworkManager.js b/lib/NetworkManager.js
index e82f2596..623d8c8f 100644
--- a/lib/NetworkManager.js
+++ b/lib/NetworkManager.js
@@ -114,6 +114,10 @@ class NetworkManager extends EventEmitter {
    */
   _onLoadingFinished(event) {
     let request = this._idToRequest.get(event.requestId);
+    // For certain requestIds we never receive requestWillBeSent event.
+    // @see https://github.com/GoogleChrome/puppeteer/issues/168
+    if (!request)
+      return;
     this._idToRequest.delete(event.requestId);
     this.emit(NetworkManager.Events.RequestFinished, request);
   }
@@ -123,6 +127,10 @@ class NetworkManager extends EventEmitter {
    */
   _onLoadingFailed(event) {
     let request = this._idToRequest.get(event.requestId);
+    // For certain requestIds we never receive requestWillBeSent event.
+    // @see https://github.com/GoogleChrome/puppeteer/issues/168
+    if (!request)
+      return;
     this._idToRequest.delete(event.requestId);
     this.emit(NetworkManager.Events.RequestFailed, request);
   }
diff --git a/test/test.js b/test/test.js
index a0b39e13..f95bf7de 100644
--- a/test/test.js
+++ b/test/test.js
@@ -457,6 +457,9 @@ describe('Puppeteer', function() {
       expect(error.message).toContain('Cannot navigate to invalid URL');
     }));
     it('should fail when navigating to bad SSL', SX(async function() {
+      page.on('request', request => expect(request).toBeTruthy());
+      page.on('requestfinished', request => expect(request).toBeTruthy());
+      page.on('requestfailed', request => expect(request).toBeTruthy());
       let error = null;
       try {
         await page.navigate(HTTPS_PREFIX + '/empty.html');