diff --git a/webrtc/base/sequenced_task_checker_impl.cc b/webrtc/base/sequenced_task_checker_impl.cc
index 615f44c2b5..f03e0b6796 100644
--- a/webrtc/base/sequenced_task_checker_impl.cc
+++ b/webrtc/base/sequenced_task_checker_impl.cc
@@ -10,6 +10,10 @@
 
 #include "webrtc/base/sequenced_task_checker_impl.h"
 
+#if defined(WEBRTC_MAC)
+#include <dispatch/dispatch.h>
+#endif
+
 #include "webrtc/base/platform_thread.h"
 #include "webrtc/base/sequenced_task_checker.h"
 #include "webrtc/base/task_queue.h"
@@ -22,7 +26,13 @@ SequencedTaskCheckerImpl::SequencedTaskCheckerImpl()
 SequencedTaskCheckerImpl::~SequencedTaskCheckerImpl() {}
 
 bool SequencedTaskCheckerImpl::CalledSequentially() const {
-  TaskQueue* current_queue = TaskQueue::Current();
+  QueueId current_queue = TaskQueue::Current();
+#if defined(WEBRTC_MAC)
+  // If we're not running on a TaskQueue, use the system dispatch queue
+  // label as an identifier.
+  if (current_queue == nullptr)
+    current_queue = dispatch_queue_get_label(DISPATCH_CURRENT_QUEUE_LABEL);
+#endif
   CritScope scoped_lock(&lock_);
   if (!attached_) {  // true if previously detached.
     valid_queue_ = current_queue;
diff --git a/webrtc/base/sequenced_task_checker_impl.h b/webrtc/base/sequenced_task_checker_impl.h
index 96cb32de6d..684b1dc502 100644
--- a/webrtc/base/sequenced_task_checker_impl.h
+++ b/webrtc/base/sequenced_task_checker_impl.h
@@ -34,10 +34,11 @@ class SequencedTaskCheckerImpl {
   void Detach();
 
  private:
+  typedef const void* QueueId;
   CriticalSection lock_;
   ThreadChecker thread_checker_;
   mutable bool attached_;
-  mutable TaskQueue* valid_queue_;
+  mutable QueueId valid_queue_;
 };
 
 }  // namespace rtc