diff --git a/uppsrc/Core/Core.h b/uppsrc/Core/Core.h
index 10c5358c2..4a437dc15 100644
--- a/uppsrc/Core/Core.h
+++ b/uppsrc/Core/Core.h
@@ -91,6 +91,9 @@
 	#else
 		#include <stdint.h>
 	#endif
+	#ifdef PLATFORM_OSX
+		#include <dispatch/dispatch.h>
+	#endif
 #endif //PLATFORM_POSIX
 
 #ifdef PLATFORM_POSIX
diff --git a/uppsrc/Core/Mt.cpp b/uppsrc/Core/Mt.cpp
index 1f8bbaa91..5342b148b 100644
--- a/uppsrc/Core/Mt.cpp
+++ b/uppsrc/Core/Mt.cpp
@@ -611,6 +611,30 @@ RWMutex::~RWMutex()
 	pthread_rwlock_destroy(rwlock);
 }
 
+#ifdef PLATFORM_OSX
+
+void Semaphore::Release()
+{
+	dispatch_semaphore_signal(sem);
+}
+
+void Semaphore::Wait()
+{
+	dispatch_semaphore_wait(sem, DISPATCH_TIME_FOREVER);
+}
+
+Semaphore::Semaphore()
+{
+	sem = dispatch_semaphore_create(0);
+}
+
+Semaphore::~Semaphore()
+{
+	dispatch_release(sem);
+}
+
+#else
+
 void Semaphore::Release()
 {
 	sem_post(&sem);
@@ -633,6 +657,8 @@ Semaphore::~Semaphore()
 
 #endif
 
+#endif
+
 void LazyUpdate::Invalidate()
 {
 	dirty.store(true, std::memory_order_release);
diff --git a/uppsrc/Core/Mt.h b/uppsrc/Core/Mt.h
index b3935d1bd..f84c32123 100644
--- a/uppsrc/Core/Mt.h
+++ b/uppsrc/Core/Mt.h
@@ -119,6 +119,8 @@ inline void AssertST() { ASSERT(Thread::IsST()); }
 class Semaphore : NoCopy {
 #ifdef PLATFORM_WIN32
 	HANDLE     handle;
+#elif PLATFORM_OSX
+	dispatch_semaphore_t    sem;
 #else
 	sem_t      sem;
 #endif
diff --git a/uppsrc/CtrlCore/CocoApp.mm b/uppsrc/CtrlCore/CocoApp.mm
index ac1f9d015..f081ed13d 100644
--- a/uppsrc/CtrlCore/CocoApp.mm
+++ b/uppsrc/CtrlCore/CocoApp.mm
@@ -84,12 +84,15 @@ bool Upp::Ctrl::ProcessEvent(bool *)
 	ASSERT(IsMainThread());
 
 	Upp::AutoreleasePool __;
-
+	
 	ONCELOCK {
 		[NSApp finishLaunching];
 	}
 	
 	NSEvent *event = GetNextEvent(nil);
+
+	// DLOG("ProcessEvent " << ToString(event.description));
+
 	if(!event)
 		return false;
 	
@@ -152,12 +155,29 @@ void Upp::Ctrl::EventLoop(Ctrl *ctrl)
 	LLOG("Leaving event loop ");
 }
 
+static std::atomic<bool> sGuiSleep;
+
 void Upp::Ctrl::GuiSleep(int ms)
 {
 	ASSERT(IsMainThread());
+	sGuiSleep = true;
 	GetNextEvent([NSDate dateWithTimeIntervalSinceNow:ms / 1000.0]);
+	sGuiSleep = false;
 }
 
+namespace Upp {
+void WakeUpGuiThread(void)
+{
+	if(sGuiSleep) {
+		sGuiSleep = false;
+		[NSApp postEvent:[NSEvent otherEventWithType:NSEventTypeApplicationDefined
+		                          location:NSMakePoint(0, 0) modifierFlags:0 timestamp:0.0
+		                          windowNumber:0 context:nil subtype: 0 data1:0 data2:0]
+		       atStart:YES];
+	}
+}
+};
+
 void  Upp::Ctrl::AnimateCaret()
 {
 	GuiLock __;
diff --git a/uppsrc/CtrlCore/CocoCtrl.cpp b/uppsrc/CtrlCore/CocoCtrl.cpp
index eff2d53dc..92d924bea 100644
--- a/uppsrc/CtrlCore/CocoCtrl.cpp
+++ b/uppsrc/CtrlCore/CocoCtrl.cpp
@@ -10,11 +10,6 @@ void ChHostSkin(void)
 {
 }
 
-void WakeUpGuiThread(void)
-{
-	
-}
-
 void Ctrl::GuiPlatformConstruct()
 {
 }
diff --git a/uppsrc/CtrlCore/CtrlMt.cpp b/uppsrc/CtrlCore/CtrlMt.cpp
index fcd18675e..ff2c799c3 100644
--- a/uppsrc/CtrlCore/CtrlMt.cpp
+++ b/uppsrc/CtrlCore/CtrlMt.cpp
@@ -74,7 +74,6 @@ struct Ctrl::CallBox {
 void Ctrl::PerformCall(Ctrl::CallBox *cbox)
 {
 	cbox->cb();
-	LLOG("Sem release");
 	cbox->sem.Release();
 }