update [patch] disclaimer in book

diff --git a/src/doc/book/src/reference/manifest.md b/src/doc/book/src/reference/manifest.md
index 8b71819c0c441501ddba97158b15fb15b1f3ea63..133d06592f13f5e8663fdb62f8dbbcf5454c13d6 100644 (file)
--- a/src/doc/book/src/reference/manifest.md
+++ b/src/doc/book/src/reference/manifest.md
@@ -727,8 +727,8 @@ source's original crate is replaced.
 
 More information about overriding dependencies can be found in the [overriding
 dependencies][replace] section of the documentation and [RFC 1969] for the
-technical specification of this feature. Note that the `[patch]` feature will
-first become available in Rust 1.20, set to be released on 2017-08-31.
+technical specification of this feature. (Note that the `[patch]` feature will
+first become available in Rust 1.21, set to be released on 2017-10-12.)
 
 [RFC 1969]: https://github.com/rust-lang/rfcs/pull/1969
 [replace]: reference/specifying-dependencies.html#overriding-dependencies