diff --git a/README.md b/README.md
index 8308816..f9cb404 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,6 @@
 # nginx-esni
 
-nginx esni test
\ No newline at end of file
+nginx esni test
+
+using [this OpenSSL](https://github.com/sftcd/openssl).
+