From cea783e5fdf3274417dd58f19aa3f5a4c757d28d Mon Sep 17 00:00:00 2001
From: steviez <steven@solana.com>
Date: Tue, 7 Sep 2021 15:01:51 -0500
Subject: [PATCH] Add note about older rust versions on release branches
 (#19681)

---
 README.md | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 09a38ece8e..d8f8c252d1 100644
--- a/README.md
+++ b/README.md
@@ -19,12 +19,18 @@ $ source $HOME/.cargo/env
 $ rustup component add rustfmt
 ```
 
-Please make sure you are always using the latest stable rust version by running:
+When building the master branch, please make sure you are using the latest stable rust version by running:
 
 ```bash
 $ rustup update
 ```
 
+When building a specific release branch, you should check the rust version in `ci/rust-version.sh` and if necessary, install that version by running:
+```bash
+$ rustup install VERSION
+```
+Note that if this is not the latest rust version on your machine, cargo commands may require an [override](https://rust-lang.github.io/rustup/overrides.html) in order to use the correct version.
+
 On Linux systems you may need to install libssl-dev, pkg-config, zlib1g-dev, etc.  On Ubuntu:
 
 ```bash