diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index a6cbb0134127d..d469f7c1722a5 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -407,22 +407,19 @@ impl<'a> Builder<'a> {
         }
     }
 
-    pub fn rustdoc(&self, compiler: Compiler) -> PathBuf {
-        self.ensure(tool::Rustdoc { target_compiler: compiler })
+    pub fn rustdoc(&self, host: Interned<String>) -> PathBuf {
+        self.ensure(tool::Rustdoc { host })
     }
 
-    pub fn rustdoc_cmd(&self, compiler: Compiler) -> Command {
+    pub fn rustdoc_cmd(&self, host: Interned<String>) -> Command {
         let mut cmd = Command::new(&self.out.join("bootstrap/debug/rustdoc"));
+        let compiler = self.compiler(self.top_stage, host);
         cmd
             .env("RUSTC_STAGE", compiler.stage.to_string())
-            .env("RUSTC_SYSROOT", if compiler.is_snapshot(&self.build) {
-                INTERNER.intern_path(self.build.rustc_snapshot_libdir())
-            } else {
-                self.sysroot(compiler)
-            })
-            .env("RUSTC_LIBDIR", self.rustc_libdir(compiler))
+            .env("RUSTC_SYSROOT", self.sysroot(compiler))
+            .env("RUSTC_LIBDIR", self.sysroot_libdir(compiler, self.build.build))
             .env("CFG_RELEASE_CHANNEL", &self.build.config.channel)
-            .env("RUSTDOC_REAL", self.rustdoc(compiler));
+            .env("RUSTDOC_REAL", self.rustdoc(host));
         cmd
     }
 
@@ -476,7 +473,7 @@ impl<'a> Builder<'a> {
              .env("RUSTC_RPATH", self.config.rust_rpath.to_string())
              .env("RUSTDOC", self.out.join("bootstrap/debug/rustdoc"))
              .env("RUSTDOC_REAL", if cmd == "doc" || cmd == "test" {
-                 self.rustdoc(compiler)
+                 self.rustdoc(compiler.host)
              } else {
                  PathBuf::from("/path/to/nowhere/rustdoc/not/required")
              })
diff --git a/src/bootstrap/check.rs b/src/bootstrap/check.rs
index 0351e9b81585f..d4d6fdc5c1b7d 100644
--- a/src/bootstrap/check.rs
+++ b/src/bootstrap/check.rs
@@ -164,7 +164,7 @@ impl Step for Cargotest {
         try_run(build, cmd.arg(&build.initial_cargo)
                           .arg(&out_dir)
                           .env("RUSTC", builder.rustc(compiler))
-                          .env("RUSTDOC", builder.rustdoc(compiler)));
+                          .env("RUSTDOC", builder.rustdoc(compiler.host)));
     }
 }
 
@@ -565,7 +565,7 @@ impl Step for Compiletest {
 
         // Avoid depending on rustdoc when we don't need it.
         if mode == "rustdoc" || mode == "run-make" {
-            cmd.arg("--rustdoc-path").arg(builder.rustdoc(compiler));
+            cmd.arg("--rustdoc-path").arg(builder.rustdoc(compiler.host));
         }
 
         cmd.arg("--src-base").arg(build.src.join("src/test").join(suite));
@@ -814,7 +814,7 @@ fn markdown_test(builder: &Builder, compiler: Compiler, markdown: &Path) {
     }
 
     println!("doc tests for: {}", markdown.display());
-    let mut cmd = builder.rustdoc_cmd(compiler);
+    let mut cmd = builder.rustdoc_cmd(compiler.host);
     build.add_rust_test_threads(&mut cmd);
     cmd.arg("--test");
     cmd.arg(markdown);
diff --git a/src/bootstrap/dist.rs b/src/bootstrap/dist.rs
index e467ba49b9734..bfcfb5f9a37f8 100644
--- a/src/bootstrap/dist.rs
+++ b/src/bootstrap/dist.rs
@@ -413,8 +413,7 @@ impl Step for Rustc {
             t!(fs::create_dir_all(image.join("bin")));
             cp_r(&src.join("bin"), &image.join("bin"));
 
-            install(&builder.ensure(tool::Rustdoc { target_compiler: compiler }),
-                &image.join("bin"), 0o755);
+            install(&builder.rustdoc(compiler.host), &image.join("bin"), 0o755);
 
             // Copy runtime DLLs needed by the compiler
             if libdir != "bin" {
diff --git a/src/bootstrap/doc.rs b/src/bootstrap/doc.rs
index 1ee578bb62b19..f0e0874abed60 100644
--- a/src/bootstrap/doc.rs
+++ b/src/bootstrap/doc.rs
@@ -260,7 +260,7 @@ fn invoke_rustdoc(builder: &Builder, compiler: Compiler, target: Interned<String
         t!(t!(File::create(&version_info)).write_all(info.as_bytes()));
     }
 
-    let mut cmd = builder.rustdoc_cmd(compiler);
+    let mut cmd = builder.rustdoc_cmd(compiler.host);
 
     let out = out.join("book");
 
@@ -343,7 +343,7 @@ impl Step for Standalone {
             }
 
             let html = out.join(filename).with_extension("html");
-            let rustdoc = builder.rustdoc(compiler);
+            let rustdoc = builder.rustdoc(compiler.host);
             if up_to_date(&path, &html) &&
                up_to_date(&footer, &html) &&
                up_to_date(&favicon, &html) &&
@@ -353,7 +353,7 @@ impl Step for Standalone {
                 continue
             }
 
-            let mut cmd = builder.rustdoc_cmd(compiler);
+            let mut cmd = builder.rustdoc_cmd(compiler.host);
             cmd.arg("--html-after-content").arg(&footer)
                .arg("--html-before-content").arg(&version_info)
                .arg("--html-in-header").arg(&favicon)
@@ -408,7 +408,7 @@ impl Step for Std {
         let out = build.doc_out(target);
         t!(fs::create_dir_all(&out));
         let compiler = builder.compiler(stage, build.build);
-        let rustdoc = builder.rustdoc(compiler);
+        let rustdoc = builder.rustdoc(compiler.host);
         let compiler = if build.force_use_stage1(compiler, target) {
             builder.compiler(1, compiler.host)
         } else {
@@ -493,7 +493,7 @@ impl Step for Test {
         let out = build.doc_out(target);
         t!(fs::create_dir_all(&out));
         let compiler = builder.compiler(stage, build.build);
-        let rustdoc = builder.rustdoc(compiler);
+        let rustdoc = builder.rustdoc(compiler.host);
         let compiler = if build.force_use_stage1(compiler, target) {
             builder.compiler(1, compiler.host)
         } else {
@@ -554,7 +554,7 @@ impl Step for Rustc {
         let out = build.doc_out(target);
         t!(fs::create_dir_all(&out));
         let compiler = builder.compiler(stage, build.build);
-        let rustdoc = builder.rustdoc(compiler);
+        let rustdoc = builder.rustdoc(compiler.host);
         let compiler = if build.force_use_stage1(compiler, target) {
             builder.compiler(1, compiler.host)
         } else {
diff --git a/src/bootstrap/tool.rs b/src/bootstrap/tool.rs
index e5783e346f46d..89b1b1137973c 100644
--- a/src/bootstrap/tool.rs
+++ b/src/bootstrap/tool.rs
@@ -236,7 +236,7 @@ impl Step for RemoteTestServer {
 
 #[derive(Debug, Copy, Clone, Hash, PartialEq, Eq)]
 pub struct Rustdoc {
-    pub target_compiler: Compiler,
+    pub host: Interned<String>,
 }
 
 impl Step for Rustdoc {
@@ -250,13 +250,13 @@ impl Step for Rustdoc {
 
     fn make_run(run: RunConfig) {
         run.builder.ensure(Rustdoc {
-            target_compiler: run.builder.compiler(run.builder.top_stage, run.host),
+            host: run.host,
         });
     }
 
     fn run(self, builder: &Builder) -> PathBuf {
         let build = builder.build;
-        let target_compiler = self.target_compiler;
+        let target_compiler = builder.compiler(builder.top_stage, self.host);
         let target = target_compiler.host;
         let build_compiler = if target_compiler.stage == 0 {
             builder.compiler(0, builder.build.build)