diff --git a/Cargo.toml b/Cargo.toml
index 2781d7c..f7a838c 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -2,6 +2,7 @@
 name = "itoa"
 version = "0.4.8" # remember to update html_root_url
 authors = ["David Tolnay <dtolnay@gmail.com>"]
+rust-version = "1.0"
 license = "MIT OR Apache-2.0"
 description = "Fast functions for printing integer primitives to an io::Write"
 repository = "https://github.com/dtolnay/itoa"