diff --git a/README.md b/README.md
index 8751177..b1548a0 100644
--- a/README.md
+++ b/README.md
@@ -2,7 +2,7 @@
 
 [![crate](https://img.shields.io/crates/v/num-bigint-dig.svg)](https://crates.io/crates/num-bigint-dig)
 [![documentation](https://docs.rs/num-bigint-dig/badge.svg)](https://docs.rs/num-bigint-dig)
-![minimum rustc 1.15](https://img.shields.io/badge/rustc-1.15+-red.svg)
+![minimum rustc 1.31](https://img.shields.io/badge/rustc-1.31+-red.svg)
 [![Travis status](https://travis-ci.org/dignifiedquire/num-bigint.svg?branch=master)](https://travis-ci.org/dignifiedquire/num-bigint)
 
 Big integer types for Rust, `BigInt` and `BigUint`.