diff --git a/src/bootstrap/tool.rs b/src/bootstrap/tool.rs
index 9fd20386e367b..7f24768a4f10e 100644
--- a/src/bootstrap/tool.rs
+++ b/src/bootstrap/tool.rs
@@ -289,8 +289,8 @@ fn rustbook_features() -> Vec<String> {
 macro_rules! bootstrap_tool {
     ($(
         $name:ident, $path:expr, $tool_name:expr
-        $(,llvm_tools = $llvm:expr)*
         $(,is_external_tool = $external:expr)*
+        $(,is_unstable_tool = $unstable:expr)*
         $(,features = $features:expr)*
         ;
     )+) => {
@@ -301,15 +301,6 @@ macro_rules! bootstrap_tool {
             )+
         }
 
-        impl Tool {
-            /// Whether this tool requires LLVM to run
-            pub fn uses_llvm_tools(&self) -> bool {
-                match self {
-                    $(Tool::$name => false $(|| $llvm)*,)+
-                }
-            }
-        }
-
         impl<'a> Builder<'a> {
             pub fn tool_exe(&self, tool: Tool) -> PathBuf {
                 match tool {
@@ -350,7 +341,12 @@ macro_rules! bootstrap_tool {
                     compiler: self.compiler,
                     target: self.target,
                     tool: $tool_name,
-                    mode: Mode::ToolBootstrap,
+                    mode: if false $(|| $unstable)* {
+                        // use in-tree libraries for unstable features
+                        Mode::ToolStd
+                    } else {
+                        Mode::ToolBootstrap
+                    },
                     path: $path,
                     is_optional_tool: false,
                     source_type: if false $(|| $external)* {
@@ -377,7 +373,7 @@ bootstrap_tool!(
     Tidy, "src/tools/tidy", "tidy";
     Linkchecker, "src/tools/linkchecker", "linkchecker";
     CargoTest, "src/tools/cargotest", "cargotest";
-    Compiletest, "src/tools/compiletest", "compiletest", llvm_tools = true;
+    Compiletest, "src/tools/compiletest", "compiletest", is_unstable_tool = true;
     BuildManifest, "src/tools/build-manifest", "build-manifest";
     RemoteTestClient, "src/tools/remote-test-client", "remote-test-client";
     RustInstaller, "src/tools/rust-installer", "fabricate", is_external_tool = true;
diff --git a/src/tools/compiletest/src/main.rs b/src/tools/compiletest/src/main.rs
index da1e3760e010d..0642823404aed 100644
--- a/src/tools/compiletest/src/main.rs
+++ b/src/tools/compiletest/src/main.rs
@@ -1,6 +1,8 @@
 #![crate_name = "compiletest"]
-#![feature(test)]
 #![deny(warnings)]
+// The `test` crate is the only unstable feature
+// allowed here, just to share similar code.
+#![feature(test)]
 
 extern crate test;