diff --git a/src/bootstrap/src/lib.rs b/src/bootstrap/src/lib.rs
index 8312885915c..cde090637e0 100644
--- a/src/bootstrap/src/lib.rs
+++ b/src/bootstrap/src/lib.rs
@@ -469,7 +469,8 @@ pub fn new(mut config: Config) -> Build {
 
             // Make sure we update these before gathering metadata so we don't get an error about missing
             // Cargo.toml files.
-            let rust_submodules = ["src/tools/cargo", "library/backtrace", "library/stdarch"];
+            let rust_submodules =
+                ["src/tools/cargo", "src/doc/book", "library/backtrace", "library/stdarch"];
             for s in rust_submodules {
                 build.update_submodule(Path::new(s));
             }