diff --git a/library/std/build.rs b/library/std/build.rs
index 0fb03c8e88a..d0b37940936 100644
--- a/library/std/build.rs
+++ b/library/std/build.rs
@@ -36,6 +36,8 @@ fn main() {
         || target.contains("nintendo-3ds")
         || target.contains("vita")
         || target.contains("nto")
+        // See src/bootstrap/synthetic_targets.rs
+        || env::var("RUSTC_BOOTSTRAP_SYNTHETIC_TARGET").is_ok()
     {
         // These platforms don't have any special requirements.
     } else {
diff --git a/src/bootstrap/compile.rs b/src/bootstrap/compile.rs
index 8f2e7d75523..14c3ef79a78 100644
--- a/src/bootstrap/compile.rs
+++ b/src/bootstrap/compile.rs
@@ -169,6 +169,11 @@ fn run(self, builder: &Builder<'_>) {
             cargo.arg("-p").arg(krate);
         }
 
+        // See src/bootstrap/synthetic_targets.rs
+        if target.is_synthetic() {
+            cargo.env("RUSTC_BOOTSTRAP_SYNTHETIC_TARGET", "1");
+        }
+
         let _guard = builder.msg(
             Kind::Build,
             compiler.stage,