diff --git a/circle.yml b/circle.yml
index a9abf4c..7989a72 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,5 +1,3 @@
-notify:
-  webhooks:
-    # A list of hook hashes, containing the url field
-    # gitter hook
-    - url: https://webhooks.gitter.im/e/9ebf3297ec153cdb0d0b
+machine:
+  node:
+    version: 4
\ No newline at end of file
diff --git a/package.json b/package.json
index 7169cc4..85b22a9 100644
--- a/package.json
+++ b/package.json
@@ -21,6 +21,9 @@
   "licenses": {
     "type": "MIT"
   },
+  "engines": {
+    "node": ">=4"
+  },
   "dependencies": {
     "babel-runtime": "^6.5.0",
     "diamond-square": "0.0.0",