diff --git a/os/osx/event_queue.h b/os/osx/event_queue.h
index a6b96736f..74d74998b 100644
--- a/os/osx/event_queue.h
+++ b/os/osx/event_queue.h
@@ -13,8 +13,6 @@
 #include "os/event.h"
 #include "os/event_queue.h"
 
-#include <atomic>
-
 namespace os {
 
 class EventQueueOSX : public EventQueue {
@@ -29,7 +27,8 @@ class EventQueueOSX : public EventQueue {
   void wakeUpQueue();
 
   base::concurrent_queue<Event> m_events;
-  std::atomic<bool> m_sleeping;
+  mutable std::mutex m_mutex;
+  bool m_sleeping;
 };
 
 using EventQueueImpl = EventQueueOSX;
diff --git a/os/osx/event_queue.mm b/os/osx/event_queue.mm
index 419fb2949..51d11cb1e 100644
--- a/os/osx/event_queue.mm
+++ b/os/osx/event_queue.mm
@@ -74,17 +74,21 @@
       }
     } while (event);
 
+    m_mutex.lock();
     if (!m_events.try_pop(ev)) {
       if (timeout == kWithoutTimeout)
         EV_TRACE("EV: Waiting for events\n");
 
       // Wait until there is a Cocoa event in queue
       m_sleeping = true;
+      m_mutex.unlock();
       event = [app nextEventMatchingMask:NSEventMaskAny
                                untilDate:untilDate
                                   inMode:NSDefaultRunLoopMode
                                  dequeue:YES];
+      m_mutex.lock();
       m_sleeping = false;
+      m_mutex.unlock();
 
       if (event) {
         EV_TRACE("EV: Event received!\n");
@@ -94,11 +98,13 @@
         EV_TRACE("EV: Timeout!");
       }
     }
+    m_mutex.unlock();
   }
 }
 
 void EventQueueOSX::queueEvent(const Event& ev)
 {
+  const std::lock_guard lock(m_mutex);
   if (m_sleeping) {
     // Wake up the macOS event queue. This is necessary in case that we
     // change the display color profile from macOS settings: the