diff --git a/addon-test-support/@ember/test-helpers/settled.js b/addon-test-support/@ember/test-helpers/settled.js
index c76ef1b75..b61ee959c 100644
--- a/addon-test-support/@ember/test-helpers/settled.js
+++ b/addon-test-support/@ember/test-helpers/settled.js
@@ -79,6 +79,13 @@ function decrementAjaxPendingRequests(event, xhr) {
   @private
 */
 export function _teardownAJAXHooks() {
+  // jQuery will not invoke `ajaxComplete` if
+  //    1. `transport.send` throws synchronously and
+  //    2. it has an `error` option which also throws synchronously
+
+  // We can no longer handle any remaining requests
+  requests = [];
+
   if (!jQuery) {
     return;
   }
diff --git a/package.json b/package.json
index 68612d815..8a71a9afd 100644
--- a/package.json
+++ b/package.json
@@ -90,4 +90,4 @@
     "**/sane": "^2.5.2",
     "ember-cli/testem": "~2.6.0"
   }
-}
+}
\ No newline at end of file
diff --git a/tests/helpers/ajax.js b/tests/helpers/ajax.js
index fd2801712..4602da5fa 100644
--- a/tests/helpers/ajax.js
+++ b/tests/helpers/ajax.js
@@ -2,13 +2,16 @@ import { Promise } from 'rsvp';
 import hasjQuery from '../helpers/has-jquery';
 import $ from 'jquery'; // FYI - not present in all scenarios
 import require from 'require';
+import { join } from '@ember/runloop';
 
 export default function ajax(url) {
   if (hasjQuery()) {
     return new Promise((resolve, reject) => {
       $.ajax(url, {
         success: resolve,
-        error: reject,
+        error(reason) {
+          join(null, reject, reason);
+        },
         cache: false,
       });
     });
diff --git a/tests/helpers/qunit-module-for.js b/tests/helpers/qunit-module-for.js
index 3a70575f1..db78f2e1b 100644
--- a/tests/helpers/qunit-module-for.js
+++ b/tests/helpers/qunit-module-for.js
@@ -18,6 +18,7 @@ export default function qunitModuleFor(testModule) {
     },
     afterEach(assert) {
       return testModule.teardown(assert).finally(() => {
+        Ember.Test.adapter = null;
         if (Ember.testing) {
           throw new Error('should not have Ember.testing === true after tests have finished');
         }
diff --git a/tests/test-helper.js b/tests/test-helper.js
index 105917a1d..fddf83230 100644
--- a/tests/test-helper.js
+++ b/tests/test-helper.js
@@ -2,6 +2,7 @@ import QUnit from 'qunit';
 import { registerDeprecationHandler } from '@ember/debug';
 import AbstractTestLoader from 'ember-cli-test-loader/test-support/index';
 import Ember from 'ember';
+import { isSettled, getSettledState } from '@ember/test-helpers';
 
 if (QUnit.config.seed) {
   QUnit.config.reorder = false;
@@ -9,6 +10,7 @@ if (QUnit.config.seed) {
 
 let moduleLoadFailures = [];
 let cleanupFailures = [];
+let asyncLeakageFailures = [];
 
 QUnit.done(function() {
   if (moduleLoadFailures.length) {
@@ -18,6 +20,10 @@ QUnit.done(function() {
   if (cleanupFailures.length) {
     throw new Error('\n' + cleanupFailures.join('\n'));
   }
+
+  if (asyncLeakageFailures.length) {
+    throw new Error('\n' + asyncLeakageFailures.join('\n'));
+  }
 });
 
 class TestLoader extends AbstractTestLoader {
@@ -71,6 +77,16 @@ QUnit.testDone(function({ module, name }) {
     console.error(message);
     testElementContainer.innerHTML = expected;
   }
+
+  if (!isSettled()) {
+    let message = `Expected to be settled after ${module}: ${name}, but was \`${JSON.stringify(
+      getSettledState()
+    )}\``;
+    asyncLeakageFailures.push(message);
+
+    // eslint-disable-next-line
+    console.error(message);
+  }
 });
 
 QUnit.assert.noDeprecations = function(callback) {
diff --git a/tests/unit/teardown-context-test.js b/tests/unit/teardown-context-test.js
index f4d36eedd..dcd906e08 100644
--- a/tests/unit/teardown-context-test.js
+++ b/tests/unit/teardown-context-test.js
@@ -1,9 +1,13 @@
 import { module, test } from 'qunit';
 import Service from '@ember/service';
+import { isSettled, getSettledState } from '@ember/test-helpers';
 import { getContext, setupContext, teardownContext } from 'ember-test-helpers';
 import { setResolverRegistry } from '../helpers/resolver';
 import hasEmberVersion from 'ember-test-helpers/has-ember-version';
 import Ember from 'ember';
+import hasjQuery from '../helpers/has-jquery';
+import ajax from '../helpers/ajax';
+import Pretender from 'pretender';
 
 module('teardownContext', function(hooks) {
   if (!hasEmberVersion(2, 4)) {
@@ -12,6 +16,7 @@ module('teardownContext', function(hooks) {
 
   let context;
   hooks.beforeEach(function() {
+    this.pretender = new Pretender();
     setResolverRegistry({
       'service:foo': Service.extend({ isFoo: true }),
     });
@@ -19,6 +24,10 @@ module('teardownContext', function(hooks) {
     return setupContext(context);
   });
 
+  hooks.afterEach(function() {
+    this.pretender.shutdown();
+  });
+
   test('it destroys any instances created', async function(assert) {
     let instance = context.owner.lookup('service:foo');
     assert.notOk(instance.isDestroyed, 'precond - not destroyed');
@@ -45,4 +54,21 @@ module('teardownContext', function(hooks) {
 
     assert.strictEqual(getContext(), undefined, 'context is unset');
   });
+
+  if (hasjQuery()) {
+    test('out of balance xhr semaphores are cleaned up on teardown', async function(assert) {
+      this.pretender.unhandledRequest = function(/* verb, path, request */) {
+        throw new Error(`Synchronous error from Pretender.prototype.unhandledRequest`);
+      };
+
+      ajax('/some/totally/invalid/url');
+
+      await teardownContext(context);
+
+      assert.ok(
+        isSettled(),
+        `out of balance xhr semaphores are cleaned up on teardown: ${getSettledState()}`
+      );
+    });
+  }
 });