diff --git a/src/shared/util.js b/src/shared/util.js
index daac2f9c3..29993afd7 100644
--- a/src/shared/util.js
+++ b/src/shared/util.js
@@ -972,23 +972,36 @@ function isSpace(ch) {
  * Promise Capability object.
  *
  * @typedef {Object} PromiseCapability
- * @property {Promise} promise - A promise object.
- * @property {function} resolve - Fulfills the promise.
- * @property {function} reject - Rejects the promise.
+ * @property {Promise} promise - A Promise object.
+ * @property {boolean} settled - If the Promise has been fulfilled/rejected.
+ * @property {function} resolve - Fulfills the Promise.
+ * @property {function} reject - Rejects the Promise.
  */
 
 /**
  * Creates a promise capability object.
  * @alias createPromiseCapability
  *
- * @return {PromiseCapability} A capability object contains:
- * - a Promise, resolve and reject methods.
+ * @return {PromiseCapability}
  */
 function createPromiseCapability() {
-  var capability = {};
-  capability.promise = new Promise(function (resolve, reject) {
-    capability.resolve = resolve;
-    capability.reject = reject;
+  const capability = Object.create(null);
+  let isSettled = false;
+
+  Object.defineProperty(capability, 'settled', {
+    get() {
+      return isSettled;
+    },
+  });
+  capability.promise = new Promise(function(resolve, reject) {
+    capability.resolve = function(data) {
+      isSettled = true;
+      resolve(data);
+    };
+    capability.reject = function(reason) {
+      isSettled = true;
+      reject(reason);
+    };
   });
   return capability;
 }
diff --git a/test/unit/api_spec.js b/test/unit/api_spec.js
index e66e653e8..025d1158b 100644
--- a/test/unit/api_spec.js
+++ b/test/unit/api_spec.js
@@ -64,14 +64,11 @@ describe('api', function() {
     it('creates pdf doc from URL', function(done) {
       var loadingTask = getDocument(basicApiGetDocumentParams);
 
-      var isProgressReportedResolved = false;
       var progressReportedCapability = createPromiseCapability();
-
       // Attach the callback that is used to report loading progress;
       // similarly to how viewer.js works.
       loadingTask.onProgress = function (progressData) {
-        if (!isProgressReportedResolved) {
-          isProgressReportedResolved = true;
+        if (!progressReportedCapability.settled) {
           progressReportedCapability.resolve(progressData);
         }
       };
@@ -183,25 +180,20 @@ describe('api', function() {
         function (done) {
       var loadingTask = getDocument(buildGetDocumentParams('pr6531_1.pdf'));
 
-      var isPasswordNeededResolved = false;
       var passwordNeededCapability = createPromiseCapability();
-      var isPasswordIncorrectResolved = false;
       var passwordIncorrectCapability = createPromiseCapability();
-
       // Attach the callback that is used to request a password;
       // similarly to how viewer.js handles passwords.
       loadingTask.onPassword = function (updatePassword, reason) {
         if (reason === PasswordResponses.NEED_PASSWORD &&
-            !isPasswordNeededResolved) {
-          isPasswordNeededResolved = true;
+            !passwordNeededCapability.settled) {
           passwordNeededCapability.resolve();
 
           updatePassword('qwerty'); // Provide an incorrect password.
           return;
         }
         if (reason === PasswordResponses.INCORRECT_PASSWORD &&
-            !isPasswordIncorrectResolved) {
-          isPasswordIncorrectResolved = true;
+            !passwordIncorrectCapability.settled) {
           passwordIncorrectCapability.resolve();
 
           updatePassword('asdfasdf'); // Provide the correct password.
diff --git a/test/unit/util_spec.js b/test/unit/util_spec.js
index f61a835dd..4d67f5815 100644
--- a/test/unit/util_spec.js
+++ b/test/unit/util_spec.js
@@ -14,9 +14,10 @@
  */
 
 import {
-  bytesToString, createValidAbsoluteUrl, getInheritableProperty, isArrayBuffer,
-  isBool, isEmptyObj, isNum, isSameOrigin, isSpace, isString, log2,
-  ReadableStream, removeNullCharacters, stringToBytes, stringToPDFString, URL
+  bytesToString, createPromiseCapability, createValidAbsoluteUrl,
+  getInheritableProperty, isArrayBuffer, isBool, isEmptyObj, isNum,
+  isSameOrigin, isSpace, isString, log2, ReadableStream, removeNullCharacters,
+  stringToBytes, stringToPDFString, URL
 } from '../../src/shared/util';
 import { Dict, Ref } from '../../src/core/primitives';
 import { XRefMock } from './test_utils';
@@ -384,4 +385,35 @@ describe('util', function() {
         .toEqual(null);
     });
   });
+
+  describe('createPromiseCapability', function() {
+    it('should resolve with correct data', function(done) {
+      const promiseCapability = createPromiseCapability();
+      expect(promiseCapability.settled).toEqual(false);
+
+      promiseCapability.resolve({ test: 'abc', });
+
+      promiseCapability.promise.then(function(data) {
+        expect(promiseCapability.settled).toEqual(true);
+
+        expect(data).toEqual({ test: 'abc', });
+        done();
+      }, done.fail);
+    });
+
+    it('should reject with correct reason', function(done) {
+      const promiseCapability = createPromiseCapability();
+      expect(promiseCapability.settled).toEqual(false);
+
+      promiseCapability.reject(new Error('reason'));
+
+      promiseCapability.promise.then(done.fail, function(reason) {
+        expect(promiseCapability.settled).toEqual(true);
+
+        expect(reason instanceof Error).toEqual(true);
+        expect(reason.message).toEqual('reason');
+        done();
+      });
+    });
+  });
 });
diff --git a/web/base_viewer.js b/web/base_viewer.js
index d3f03214c..416602dca 100644
--- a/web/base_viewer.js
+++ b/web/base_viewer.js
@@ -395,8 +395,7 @@ class BaseViewer {
       });
     });
 
-    let isOnePageRenderedResolved = false;
-    let onePageRenderedCapability = createPromiseCapability();
+    const onePageRenderedCapability = createPromiseCapability();
     this.onePageRendered = onePageRenderedCapability.promise;
 
     let bindOnAfterAndBeforeDraw = (pageView) => {
@@ -407,8 +406,7 @@ class BaseViewer {
         this._buffer.push(pageView);
       };
       pageView.onAfterDraw = () => {
-        if (!isOnePageRenderedResolved) {
-          isOnePageRenderedResolved = true;
+        if (!onePageRenderedCapability.settled) {
           onePageRenderedCapability.resolve();
         }
       };