diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index 26bcaf134567..da87b3bfe0cd 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -70,9 +70,11 @@ pub fn book(build: &Build, target: &str, name: &str) {
 
     // build the index page
     let index = format!("{}/index.md", name);
+    println!("Documenting book index ({})", target);
     invoke_rustdoc(build, target, &index);
     
     // build the redirect pages
+    println!("Documenting book redirect pages ({})", target);
     for file in t!(fs::read_dir(build.src.join("src/doc/book/redirects"))) {
         let file = t!(file);
         let path = file.path();
@@ -93,16 +95,27 @@ fn invoke_rustdoc(build: &Build, target: &str, markdown: &str) {
 
     let favicon = build.src.join("src/doc/favicon.inc");
     let footer = build.src.join("src/doc/footer.inc");
-    t!(fs::copy(build.src.join("src/doc/rust.css"), out.join("rust.css")));
 
+    let version_input = build.src.join("src/doc/version_info.html.template");
     let version_info = out.join("version_info.html");
 
+    if !up_to_date(&version_input, &version_info) {
+        let mut info = String::new();
+        t!(t!(File::open(&version_input)).read_to_string(&mut info));
+        let info = info.replace("VERSION", &build.rust_release())
+                       .replace("SHORT_HASH", build.rust_info.sha_short().unwrap_or(""))
+                       .replace("STAMP", build.rust_info.sha().unwrap_or(""));
+        t!(t!(File::create(&version_info)).write_all(info.as_bytes()));
+    }
+
     let mut cmd = Command::new(&rustdoc);
 
     build.add_rustc_lib_path(&compiler, &mut cmd);
 
     let out = out.join("book");
 
+    t!(fs::copy(build.src.join("src/doc/rust.css"), out.join("rust.css")));
+
     cmd.arg("--html-after-content").arg(&footer)
         .arg("--html-before-content").arg(&version_info)
         .arg("--html-in-header").arg(&favicon)