diff --git a/README.md b/README.md
index 2f7462c..caa8431 100644
--- a/README.md
+++ b/README.md
@@ -43,6 +43,8 @@ Install
 npm install --save letsencrypt-express@2.x
 ```
 
+**Important**: Use node v4.5+ or v6.x, node <= v4.4 has a [known bug](https://github.com/nodejs/node/issues/8053) in the `Buffer` implementation.
+
 QuickStart
 ==========