diff --git a/uppsrc/Core/CoWork.cpp b/uppsrc/Core/CoWork.cpp
index a832f9785..c6f5bf321 100644
--- a/uppsrc/Core/CoWork.cpp
+++ b/uppsrc/Core/CoWork.cpp
@@ -58,8 +58,7 @@ CoWork::Pool::~Pool()
 	jobs[0].work = NULL;
 	scheduled = 1;
 	lock.Leave();
-	for(int i = 0; i < threads.GetCount(); i++)
-		waitforjob.Release();
+	waitforjob.Broadcast();
 	for(int i = 0; i < threads.GetCount(); i++)
 		threads[i].Wait();
 	LLOG("Quit ended");
@@ -90,7 +89,7 @@ bool CoWork::Pool::DoJob()
 		p.lock.Enter();
 	if(--work->todo == 0) {
 		LLOG("Releasing waitforfinish of (CoWork " << FormatIntHex(work) << ")");
-		work->waitforfinish.Release();
+		work->waitforfinish.Signal();
 	}
 	LLOG("DoJobA " << p.scheduled << ", todo: " << work->todo << " (CoWork " << FormatIntHex(work) << ")");
 	ASSERT(work->todo >= 0);
@@ -107,11 +106,9 @@ void CoWork::Pool::ThreadRun(int tno)
 		while(p.scheduled == 0) {
 			LHITCOUNT("CoWork: Parking thread to Wait");
 			p.waiting_threads++;
-			p.lock.Leave();
 			LLOG("#" << tno << " Waiting for job");
-			p.waitforjob.Wait();
+			p.waitforjob.Wait(p.lock);
 			LLOG("#" << tno << " Waiting ended");
-			p.lock.Enter();
 		}
 		LLOG("#" << tno << " Job acquired");
 		LHITCOUNT("CoWork: Running new job");
@@ -145,7 +142,7 @@ void CoWork::Do(Function<void ()>&& fn)
 	if(p.waiting_threads) {
 		LLOG("Releasing thread waiting for job: " << p.waiting_threads);
 		p.waiting_threads--;
-		p.waitforjob.Release();
+		p.waitforjob.Signal();
 	}
 	p.lock.Leave();
 }
@@ -191,10 +188,8 @@ void CoWork::Finish() {
 		if(p.scheduled)
 			Pool::DoJob();
 		else {
-			p.lock.Leave();
 			LLOG("WaitForFinish (CoWork " << FormatIntHex(this) << ")");
-			waitforfinish.Wait();
-			p.lock.Enter();
+			waitforfinish.Wait(p.lock);
 		}
 	}
 	p.lock.Leave();
diff --git a/uppsrc/Core/CoWork.h b/uppsrc/Core/CoWork.h
index 5cb4d35ec..c199fdeeb 100644
--- a/uppsrc/Core/CoWork.h
+++ b/uppsrc/Core/CoWork.h
@@ -17,8 +17,8 @@ public:
 		int             waiting_threads;
 		Array<Thread>   threads;
 
-		Mutex           lock;
-		Semaphore       waitforjob;
+		Mutex             lock;
+		ConditionVariable waitforjob;
 
 		Pool(int nthreads);
 		~Pool();
@@ -37,8 +37,8 @@ public:
 	static thread_local bool is_worker;
 	static thread_local Pool *pool;
 
-	Semaphore waitforfinish;
-	int       todo;
+	ConditionVariable waitforfinish;
+	int               todo;
 
 	Mutex stepmutex;
 	Array<BiVector<Function<void ()>>> step;
diff --git a/uppsrc/plugin/lz4/lz4.h b/uppsrc/plugin/lz4/lz4.h
index c067c442e..190674583 100644
--- a/uppsrc/plugin/lz4/lz4.h
+++ b/uppsrc/plugin/lz4/lz4.h
@@ -24,6 +24,10 @@ class Lz4 {
 	String       header_data;
 
     String       out;
+
+	
+	bool         co;
+	
     
     void          TryHeader();
 
@@ -47,6 +51,8 @@ public:
 
 	void Compress();
 	void Decompress();
+	
+	void Co(bool b)                        { co = b; }
 
 	bool   IsError() const                 { return error; }