diff --git a/lib/utils/errors.js b/lib/utils/errors.js
--- a/lib/utils/errors.js
+++ b/lib/utils/errors.js
@@ -42,7 +42,9 @@
 }
 
 function getMessageForException(e: mixed): ?string {
-  if (
+  if (typeof e === 'string') {
+    return e;
+  } else if (
     e &&
     typeof e === 'object' &&
     e.message &&