diff --git a/docs/book/src/building_crosvm/index.md b/docs/book/src/building_crosvm/index.md
index d43218d766..ad28c191a9 100644
--- a/docs/book/src/building_crosvm/index.md
+++ b/docs/book/src/building_crosvm/index.md
@@ -2,6 +2,8 @@
 
 This chapter describes how to build crosvm on each host OS:
 
+Pre-requisite: install [Rust](https://www.rust-lang.org/).
+
 - [Linux](./linux.md)
 - [Windows](./windows.md)