diff --git a/src/bootstrap/src/core/build_steps/test.rs b/src/bootstrap/src/core/build_steps/test.rs
index f2284b8a4ba..0668d07ed06 100644
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -1568,9 +1568,11 @@ fn run(self, builder: &Builder<'_>) {
         }
 
         if mode == "run-coverage" {
+            // The demangler doesn't need the current compiler, so we can avoid
+            // unnecessary rebuilds by using the bootstrap compiler instead.
             let rust_demangler = builder
                 .ensure(tool::RustDemangler {
-                    compiler,
+                    compiler: compiler.with_stage(0),
                     target: compiler.host,
                     extra_features: Vec::new(),
                 })