diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 2281a45e014a..ebe03596b8a1 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -1135,12 +1135,10 @@ impl<'a> Builder<'a> {
                     .env(format!("RANLIB_{}", target), ranlib);
             }
 
-            if let Ok(cxx) = self.cxx(target) {
-                let cxx = ccacheify(&cxx);
-                cargo
-                    .env(format!("CXX_{}", target), &cxx)
-                    .env(format!("CXXFLAGS_{}", target), cflags);
-            }
+            let cxx = ccacheify(&self.cxx(target));
+            cargo
+                .env(format!("CXX_{}", target), &cxx)
+                .env(format!("CXXFLAGS_{}", target), cflags);
         }
 
         if (cmd == "build" || cmd == "rustc")
diff --git a/src/bootstrap/cc_detect.rs b/src/bootstrap/cc_detect.rs
index dfc243b7054a..7cdc835f2281 100644
--- a/src/bootstrap/cc_detect.rs
+++ b/src/bootstrap/cc_detect.rs
@@ -95,30 +95,28 @@ pub fn find(build: &mut Build) {
         };
 
         build.cc.insert(target, compiler);
+        let cflags = build.cflags(target, GitRepo::Rustc);
+
+        // If we use llvm-libunwind, we will need a C++ compiler as well for all targets
+        // We'll need one anyways if the target triple is also a host triple
+        cfg.cpp(true);
+        if let Some(cxx) = config.and_then(|c| c.cxx.as_ref()) {
+            cfg.compiler(cxx);
+        } else {
+            set_compiler(&mut cfg, Language::CPlusPlus, target, config, build);
+        }
+        let compiler = cfg.get_compiler();
+        build.cxx.insert(target, compiler);
+
         build.verbose(&format!("CC_{} = {:?}", &target, build.cc(target)));
-        build.verbose(&format!("CFLAGS_{} = {:?}", &target, build.cflags(target, GitRepo::Rustc)));
+        build.verbose(&format!("CFLAGS_{} = {:?}", &target, cflags));
+        build.verbose(&format!("CXX_{} = {:?}", &target, build.cxx(target)));
+        build.verbose(&format!("CXXFLAGS_{} = {:?}", &target, cflags));
         if let Some(ar) = ar {
             build.verbose(&format!("AR_{} = {:?}", &target, ar));
             build.ar.insert(target, ar);
         }
     }
-
-    // For all host triples we need to find a C++ compiler as well
-    let hosts = build.hosts.iter().cloned().chain(iter::once(build.build)).collect::<HashSet<_>>();
-    for host in hosts.into_iter() {
-        let mut cfg = cc::Build::new();
-        cfg.cargo_metadata(false).opt_level(2).warnings(false).debug(false).cpp(true)
-           .target(&host).host(&build.build);
-        let config = build.config.target_config.get(&host);
-        if let Some(cxx) = config.and_then(|c| c.cxx.as_ref()) {
-            cfg.compiler(cxx);
-        } else {
-            set_compiler(&mut cfg, Language::CPlusPlus, host, config, build);
-        }
-        let compiler = cfg.get_compiler();
-        build.verbose(&format!("CXX_{} = {:?}", host, compiler.path()));
-        build.cxx.insert(host, compiler);
-    }
 }
 
 fn set_compiler(cfg: &mut cc::Build,
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index c7fa8e788b57..e2c741a064ff 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -782,7 +782,7 @@ pub fn build_codegen_backend(builder: &Builder<'_>,
                !target.contains("windows") &&
                !target.contains("apple") {
                 let file = compiler_file(builder,
-                                         builder.cxx(target).unwrap(),
+                                         builder.cxx(target),
                                          target,
                                          "libstdc++.a");
                 cargo.env("LLVM_STATIC_STDCPP", file);
diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index b9d287abb0c7..42fbecd8e1c7 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -815,13 +815,8 @@ impl Build {
     }
 
     /// Returns the path to the C++ compiler for the target specified.
-    fn cxx(&self, target: Interned<String>) -> Result<&Path, String> {
-        match self.cxx.get(&target) {
-            Some(p) => Ok(p.path()),
-            None => Err(format!(
-                    "target `{}` is not configured as a host, only as a target",
-                    target))
-        }
+    fn cxx(&self, target: Interned<String>) -> &Path {
+        self.cxx[&target].path()
     }
 
     /// Returns the path to the linker for the given target if it needs to be overridden.
diff --git a/src/bootstrap/native.rs b/src/bootstrap/native.rs
index bf3601cb312f..9df1870751f6 100644
--- a/src/bootstrap/native.rs
+++ b/src/bootstrap/native.rs
@@ -358,7 +358,7 @@ fn configure_cmake(builder: &Builder<'_>,
 
     let (cc, cxx) = match builder.config.llvm_clang_cl {
         Some(ref cl) => (cl.as_ref(), cl.as_ref()),
-        None => (builder.cc(target), builder.cxx(target).unwrap()),
+        None => (builder.cc(target), builder.cxx(target)),
     };
 
     // Handle msvc + ninja + ccache specially (this is what the bots use)
diff --git a/src/bootstrap/sanity.rs b/src/bootstrap/sanity.rs
index dc65fb9b7970..5bf08a45b290 100644
--- a/src/bootstrap/sanity.rs
+++ b/src/bootstrap/sanity.rs
@@ -146,7 +146,7 @@ pub fn check(build: &mut Build) {
 
     for host in &build.hosts {
         if !build.config.dry_run {
-            cmd_finder.must_have(build.cxx(*host).unwrap());
+            cmd_finder.must_have(build.cxx(*host));
         }
     }
 
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
index 74caaae2840c..095ba146caa6 100644
--- a/src/bootstrap/test.rs
+++ b/src/bootstrap/test.rs
@@ -1211,7 +1211,7 @@ impl Step for Compiletest {
                 cmd.arg("--cc")
                     .arg(builder.cc(target))
                     .arg("--cxx")
-                    .arg(builder.cxx(target).unwrap())
+                    .arg(builder.cxx(target))
                     .arg("--cflags")
                     .arg(builder.cflags(target, GitRepo::Rustc).join(" "))
                     .arg("--llvm-components")