diff --git a/.rustfmt.toml b/.rustfmt.toml
index 230ec3333..d11c488e6 100644
--- a/.rustfmt.toml
+++ b/.rustfmt.toml
@@ -1,2 +1,3 @@
+# This requires the nightly release of Rust, so when formating the repo, use
+# $ cargo +nightly fmt
 imports_granularity = "Crate"
-