diff --git a/src/bootstrap/bin/rustdoc.rs b/src/bootstrap/bin/rustdoc.rs
index 085f243785cbe..1c9f6e1ab285c 100644
--- a/src/bootstrap/bin/rustdoc.rs
+++ b/src/bootstrap/bin/rustdoc.rs
@@ -69,6 +69,17 @@ fn main() {
                .arg("unstable-options");
         }
         cmd.arg("--generate-redirect-pages");
+        has_unstable = true;
+    }
+
+    // Needed to be able to run all rustdoc tests.
+    if let Some(ref x) = env::var_os("RUSTDOC_RESOURCE_SUFFIX") {
+        // This "unstable-options" can be removed when `--resource-suffix` is stabilized
+        if !has_unstable {
+            cmd.arg("-Z")
+               .arg("unstable-options");
+        }
+        cmd.arg("--resource-suffix").arg(x);
     }
 
     if verbose > 1 {
diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index 2ea6be552106b..d831d2f1af2dd 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -343,12 +343,9 @@ fn invoke_rustdoc(
         .arg("--html-before-content").arg(&version_info)
         .arg("--html-in-header").arg(&header)
         .arg("--markdown-no-toc")
-        .arg("--markdown-playground-url")
-        .arg("https://play.rust-lang.org/")
-        .arg("-o").arg(&out)
-        .arg(&path)
-        .arg("--markdown-css")
-        .arg("../rust.css");
+        .arg("--markdown-playground-url").arg("https://play.rust-lang.org/")
+        .arg("-o").arg(&out).arg(&path)
+        .arg("--markdown-css").arg("../rust.css");
 
     builder.run(&mut cmd);
 }
@@ -431,8 +428,7 @@ impl Step for Standalone {
                .arg("--html-in-header").arg(&favicon)
                .arg("--markdown-no-toc")
                .arg("--index-page").arg(&builder.src.join("src/doc/index.md"))
-               .arg("--markdown-playground-url")
-               .arg("https://play.rust-lang.org/")
+               .arg("--markdown-playground-url").arg("https://play.rust-lang.org/")
                .arg("-o").arg(&out)
                .arg(&path);
 
@@ -523,6 +519,7 @@ impl Step for Std {
                  .arg("--markdown-css").arg("rust.css")
                  .arg("--markdown-no-toc")
                  .arg("--generate-redirect-pages")
+                 .arg("--resource-suffix").arg(crate::channel::CFG_RELEASE_NUM)
                  .arg("--index-page").arg(&builder.src.join("src/doc/index.md"));
 
             builder.run(&mut cargo);
@@ -589,6 +586,7 @@ impl Step for Test {
 
         cargo.arg("--no-deps")
              .arg("-p").arg("test")
+             .env("RUSTDOC_RESOURCE_SUFFIX", crate::channel::CFG_RELEASE_NUM)
              .env("RUSTDOC_GENERATE_REDIRECT_PAGES", "1");
 
         builder.run(&mut cargo);
@@ -660,6 +658,7 @@ impl Step for WhitelistedRustc {
         // for which docs must be built.
         for krate in &["proc_macro"] {
             cargo.arg("-p").arg(krate)
+                 .env("RUSTDOC_RESOURCE_SUFFIX", crate::channel::CFG_RELEASE_NUM)
                  .env("RUSTDOC_GENERATE_REDIRECT_PAGES", "1");
         }
 
@@ -890,6 +889,7 @@ impl Step for ErrorIndex {
         );
         index.arg("html");
         index.arg(out.join("error-index.html"));
+        index.arg(crate::channel::CFG_RELEASE_NUM);
 
         // FIXME: shouldn't have to pass this env var
         index.env("CFG_BUILD", &builder.config.build)
diff --git a/src/tools/error_index_generator/main.rs b/src/tools/error_index_generator/main.rs
index faeeea605a2b4..04986b59ea0f1 100644
--- a/src/tools/error_index_generator/main.rs
+++ b/src/tools/error_index_generator/main.rs
@@ -27,9 +27,10 @@ enum OutputFormat {
 }
 
 impl OutputFormat {
-    fn from(format: &str) -> OutputFormat {
+    fn from(format: &str, resource_suffix: &str) -> OutputFormat {
         match &*format.to_lowercase() {
-            "html"     => OutputFormat::HTML(HTMLFormatter(RefCell::new(IdMap::new()))),
+            "html"     => OutputFormat::HTML(HTMLFormatter(RefCell::new(IdMap::new()),
+                                                           resource_suffix.to_owned())),
             "markdown" => OutputFormat::Markdown(MarkdownFormatter),
             s          => OutputFormat::Unknown(s.to_owned()),
         }
@@ -44,7 +45,7 @@ trait Formatter {
     fn footer(&self, output: &mut dyn Write) -> Result<(), Box<dyn Error>>;
 }
 
-struct HTMLFormatter(RefCell<IdMap>);
+struct HTMLFormatter(RefCell<IdMap>, String);
 struct MarkdownFormatter;
 
 impl Formatter for HTMLFormatter {
@@ -55,7 +56,7 @@ impl Formatter for HTMLFormatter {
 <title>Rust Compiler Error Index</title>
 <meta charset="utf-8">
 <!-- Include rust.css after light.css so its rules take priority. -->
-<link rel="stylesheet" type="text/css" href="light.css"/>
+<link rel="stylesheet" type="text/css" href="light{suffix}.css"/>
 <link rel="stylesheet" type="text/css" href="rust.css"/>
 <style>
 .error-undescribed {{
@@ -64,7 +65,7 @@ impl Formatter for HTMLFormatter {
 </style>
 </head>
 <body>
-"##)?;
+"##, suffix=self.1)?;
         Ok(())
     }
 
@@ -242,9 +243,12 @@ fn main_with_result(format: OutputFormat, dst: &Path) -> Result<(), Box<dyn Erro
 
 fn parse_args() -> (OutputFormat, PathBuf) {
     let mut args = env::args().skip(1);
-    let format = args.next().map(|a| OutputFormat::from(&a))
-                            .unwrap_or(OutputFormat::from("html"));
-    let dst = args.next().map(PathBuf::from).unwrap_or_else(|| {
+    let format = args.next();
+    let dst = args.next();
+    let resource_suffix = args.next().unwrap_or_else(String::new);
+    let format = format.map(|a| OutputFormat::from(&a, &resource_suffix))
+                       .unwrap_or(OutputFormat::from("html", &resource_suffix));
+    let dst = dst.map(PathBuf::from).unwrap_or_else(|| {
         match format {
             OutputFormat::HTML(..) => PathBuf::from("doc/error-index.html"),
             OutputFormat::Markdown(..) => PathBuf::from("doc/error-index.md"),