diff --git a/src/sandbox.js b/src/sandbox.js
index <HASH>..<HASH> 100644
--- a/src/sandbox.js
+++ b/src/sandbox.js
@@ -19,3 +19,6 @@ afterEach(function() {
   this.sandbox.restore();
 });
 
+process.on('unhandledRejection', (err) => {
+  throw err;
+});
Throw unhandled rejections in mocha tests

Only works under >= 3.x, but will still help us potentially catch issues in test.