1 files changed, 3 insertions, 0 deletions
diff --git a/compiler/rustc_driver_impl/src/lib.rs b/compiler/rustc_driver_impl/src/lib.rs
index 9b16f246193..80a9dfd251a 100644
--- a/compiler/rustc_driver_impl/src/lib.rs
+++ b/compiler/rustc_driver_impl/src/lib.rs
@@ -256,6 +256,9 @@ fn run_compiler(
 
     let sopts = config::build_session_options(&matches);
 
+    // Set parallel mode before thread pool creation, which will create `Lock`s.
+    interface::set_thread_safe_mode(&sopts.unstable_opts);
+
     if let Some(ref code) = matches.opt_str("explain") {
         handle_explain(diagnostics_registry(), code, sopts.error_format);
         return Ok(());