diff --git a/src/librustc/session/config.rs b/src/librustc/session/config.rs
index 960bbfdd1ef71..b3f1b9c8e627c 100644
--- a/src/librustc/session/config.rs
+++ b/src/librustc/session/config.rs
@@ -1337,6 +1337,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
           "enable the experimental Chalk-based trait solving engine"),
     cross_lang_lto: CrossLangLto = (CrossLangLto::Disabled, parse_cross_lang_lto, [TRACKED],
           "generate build artifacts that are compatible with linker-based LTO."),
+    no_parallel_llvm: bool = (false, parse_bool, [UNTRACKED],
+          "don't run LLVM in parallel (while keeping codegen-units and ThinLTO)"),
 }
 
 pub fn default_lib_output() -> CrateType {
diff --git a/src/librustc_codegen_llvm/back/write.rs b/src/librustc_codegen_llvm/back/write.rs
index 1151e0131313d..baab3c618be58 100644
--- a/src/librustc_codegen_llvm/back/write.rs
+++ b/src/librustc_codegen_llvm/back/write.rs
@@ -1738,7 +1738,9 @@ fn start_executing_work(tcx: TyCtxt,
                             .binary_search_by_key(&cost, |&(_, cost)| cost)
                             .unwrap_or_else(|e| e);
                         work_items.insert(insertion_index, (work, cost));
-                        helper.request_token();
+                        if !cgcx.opts.debugging_opts.no_parallel_llvm {
+                            helper.request_token();
+                        }
                     }
                 }
 
@@ -1842,7 +1844,9 @@ fn start_executing_work(tcx: TyCtxt,
                     };
                     work_items.insert(insertion_index, (llvm_work_item, cost));
 
-                    helper.request_token();
+                    if !cgcx.opts.debugging_opts.no_parallel_llvm {
+                        helper.request_token();
+                    }
                     assert_eq!(main_thread_worker_state,
                                MainThreadWorkerState::Codegenning);
                     main_thread_worker_state = MainThreadWorkerState::Idle;