diff --git a/doc/PROTOCOL-HTTP2.md b/doc/PROTOCOL-HTTP2.md
index 1dc1ca423ed..40ec2c10331 100644
--- a/doc/PROTOCOL-HTTP2.md
+++ b/doc/PROTOCOL-HTTP2.md
@@ -4,7 +4,7 @@
 This document serves as a detailed description for an implementation of gRPC carried over <a href="https://tools.ietf.org/html/rfc7540">HTTP2 framing</a>. It assumes familiarity with the HTTP2 specification.
 
 ## Protocol
-Production rules are using <a href="http://tools.ietf.org/html/rfc5234">ABNF syntax</a>.
+Production rules are using <a href="https://tools.ietf.org/html/rfc5234">ABNF syntax</a>.
 
 ### Outline