Add a rustc version badge
diff --git a/README.md b/README.md
index 6cf18be..ab45488 100644
--- a/README.md
+++ b/README.md
@@ -4,6 +4,7 @@
 [![Build Status](https://api.travis-ci.org/dtolnay/syn.svg?branch=master)](https://travis-ci.org/dtolnay/syn)
 [![Latest Version](https://img.shields.io/crates/v/syn.svg)](https://crates.io/crates/syn)
 [![Rust Documentation](https://img.shields.io/badge/api-rustdoc-blue.svg)](https://docs.rs/syn/0.12/syn/)
+[![Rustc Version 1.15+](https://img.shields.io/badge/rustc-1.15+-lightgray.svg)](https://blog.rust-lang.org/2017/02/02/Rust-1.15.html)
 
 Syn is a parsing library for parsing a stream of Rust tokens into a syntax tree
 of Rust source code.