diff --git a/client/src/templates/Challenges/classic/Show.js b/client/src/templates/Challenges/classic/Show.js
index 18620dd494..259b192bef 100644
--- a/client/src/templates/Challenges/classic/Show.js
+++ b/client/src/templates/Challenges/classic/Show.js
@@ -34,7 +34,8 @@ import {
   updateChallengeMeta,
   challengeMounted,
   consoleOutputSelector,
-  executeChallenge
+  executeChallenge,
+  cancelTests
 } from '../redux';
 
 import './classic.css';
@@ -54,12 +55,14 @@ const mapDispatchToProps = dispatch =>
       initTests,
       updateChallengeMeta,
       challengeMounted,
-      executeChallenge
+      executeChallenge,
+      cancelTests
     },
     dispatch
   );
 
 const propTypes = {
+  cancelTests: PropTypes.func.isRequired,
   challengeMounted: PropTypes.func.isRequired,
   createFiles: PropTypes.func.isRequired,
   data: PropTypes.shape({
@@ -164,8 +167,9 @@ class ShowClassic extends Component {
   }
 
   componentWillUnmount() {
-    const { createFiles } = this.props;
+    const { createFiles, cancelTests } = this.props;
     createFiles({});
+    cancelTests();
   }
 
   getChallenge = () => this.props.data.challengeNode;
diff --git a/client/src/templates/Challenges/redux/execute-challenge-saga.js b/client/src/templates/Challenges/redux/execute-challenge-saga.js
index 54970ee726..b5048181f1 100644
--- a/client/src/templates/Challenges/redux/execute-challenge-saga.js
+++ b/client/src/templates/Challenges/redux/execute-challenge-saga.js
@@ -6,7 +6,9 @@ import {
   takeLatest,
   takeEvery,
   fork,
-  getContext
+  getContext,
+  take,
+  cancel
 } from 'redux-saga/effects';
 import { channel } from 'redux-saga';
 import escape from 'lodash/escape';
@@ -21,7 +23,8 @@ import {
   logsToConsole,
   updateTests,
   isBuildEnabledSelector,
-  disableBuildOnError
+  disableBuildOnError,
+  types
 } from './';
 
 import {
@@ -36,6 +39,13 @@ import {
 // How long before bailing out of a preview.
 const previewTimeout = 2500;
 
+export function* executeCancellableChallengeSaga() {
+  const task = yield fork(executeChallengeSaga);
+
+  yield take(types.cancelTests);
+  yield cancel(task);
+}
+
 export function* executeChallengeSaga() {
   const isBuildEnabled = yield select(isBuildEnabledSelector);
   if (!isBuildEnabled) {
@@ -181,7 +191,7 @@ function* previewChallengeSaga() {
 
 export function createExecuteChallengeSaga(types) {
   return [
-    takeLatest(types.executeChallenge, executeChallengeSaga),
+    takeLatest(types.executeChallenge, executeCancellableChallengeSaga),
     takeLatest(
       [
         types.updateFile,
diff --git a/client/src/templates/Challenges/redux/index.js b/client/src/templates/Challenges/redux/index.js
index 00d7381dbc..e8b1ff0444 100644
--- a/client/src/templates/Challenges/redux/index.js
+++ b/client/src/templates/Challenges/redux/index.js
@@ -60,6 +60,7 @@ export const types = createTypes(
     'updateSuccessMessage',
     'updateTests',
     'updateLogs',
+    'cancelTests',
 
     'logsToConsole',
 
@@ -121,6 +122,7 @@ export const createFiles = createAction(types.createFiles, challengeFiles =>
 export const createQuestion = createAction(types.createQuestion);
 export const initTests = createAction(types.initTests);
 export const updateTests = createAction(types.updateTests);
+export const cancelTests = createAction(types.cancelTests);
 
 export const initConsole = createAction(types.initConsole);
 export const initLogs = createAction(types.initLogs);