diff --git a/lib/README.http2 b/lib/README.http2
index daa63383494d0686071204654458bdc9b5f6b35c..0a397523dc5e6a595f887a73ed3337e787fa5c9d 100644
--- a/lib/README.http2
+++ b/lib/README.http2
@@ -3,6 +3,10 @@ HTTP2 with libcurl
 
  Spec: http://tools.ietf.org/html/draft-ietf-httpbis-http2
 
+ Build prerequisites
+  - nghttp2
+  - OpenSSL or NSS or GnutTLS with a new enough version
+
  nghttp2 (https://github.com/tatsuhiro-t/nghttp2)
 
   libcurl uses this 3rd party library for the low level protocol handling