diff --git a/lib/reporters/json.js b/lib/reporters/json.js
index d03712013b..dcf89e066c 100644
--- a/lib/reporters/json.js
+++ b/lib/reporters/json.js
@@ -68,7 +68,7 @@ function clean(test) {
     title: test.title,
     fullTitle: test.fullTitle(),
     duration: test.duration,
-    err: errorJSON(test.err)
+    err: errorJSON(test.err || {})
   }
 }