diff --git a/.travis.yml b/.travis.yml
index 6ec2a23..19cc1a9 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,5 +1,7 @@
 language: node_js
-node_js: 6
+node_js:
+- 6
+- 4
 install:
 - npm install --only=production
 cache: