1 files changed, 6 insertions, 0 deletions
diff --git a/README.md b/README.md
index 6bb89a25f..572b0f481 100644
--- a/README.md
+++ b/README.md
@@ -125,6 +125,12 @@ submodule. However, you need to install separately:
     # Format code.
     ./tools/format.py
 
+Before running `./tools/format.py`, make sure you have `yapf` installed for the
+current Python and `rustfmt` for Rust. They can be installed by:
+
+    pip install yapf
+    rustup component add rustfmt-preview
+
 Other useful commands:
 
     # Call ninja manually.