diff --git a/js/src/vm/HelperThreads.cpp b/js/src/vm/HelperThreads.cpp
index fb5fd5f018f6..ef50da616753 100644
--- a/js/src/vm/HelperThreads.cpp
+++ b/js/src/vm/HelperThreads.cpp
@@ -2302,6 +2302,13 @@ GlobalHelperThreadState::trace(JSTracer* trc)
         parseTask->trace(trc);
 }
 
+/* static */ void
+HelperThread::WakeupAll()
+{
+    AutoLockHelperThreadState lock;
+    HelperThreadState().notifyAll(GlobalHelperThreadState::PRODUCER, lock);
+}
+
 void
 JSContext::setHelperThread(HelperThread* thread)
 {
@@ -2395,6 +2402,19 @@ HelperThread::threadLoop()
 
         const TaskSpec* task = findHighestPriorityTask(lock);
         if (!task) {
+            if (mozilla::recordreplay::IsRecordingOrReplaying()) {
+                // Unlock the helper thread state lock before potentially
+                // blocking while the main thread waits for all threads to
+                // become idle. Otherwise we would need to see if we need to
+                // block at every point where a helper thread acquires the
+                // helper thread state lock.
+                {
+                    AutoUnlockHelperThreadState unlock(lock);
+                    mozilla::recordreplay::MaybeWaitForCheckpointSave();
+                }
+                mozilla::recordreplay::NotifyUnrecordedWait(WakeupAll);
+            }
+
             HelperThreadState().wait(lock, GlobalHelperThreadState::PRODUCER);
             continue;
         }
diff --git a/js/src/vm/HelperThreads.h b/js/src/vm/HelperThreads.h
index df19fd399fee..426ee2cbd3a3 100644
--- a/js/src/vm/HelperThreads.h
+++ b/js/src/vm/HelperThreads.h
@@ -414,6 +414,8 @@ struct HelperThread
     static void ThreadMain(void* arg);
     void threadLoop();
 
+    static void WakeupAll();
+
     void ensureRegisteredWithProfiler();
     void unregisterWithProfilerIfNeeded();