diff --git a/uppsrc/Core/App.cpp b/uppsrc/Core/App.cpp
index 28abb8920..e1bb6f64f 100644
--- a/uppsrc/Core/App.cpp
+++ b/uppsrc/Core/App.cpp
@@ -431,11 +431,7 @@ void AppInit__(int argc, const char **argv)
 
 void AppExit__()
 {
-#ifdef _MULTITHREADED
-#ifndef COWORK2
 	Thread::ShutdownThreads();
-#endif
-#endif
 	sMainRunning = false;
 #ifdef PLATFORM_POSIX
 	MemoryIgnoreLeaksBegin(); // Qt leaks on app exit...
diff --git a/uppsrc/Core/Atomic.h b/uppsrc/Core/Atomic.h
index 9578b2ef9..25909dd35 100644
--- a/uppsrc/Core/Atomic.h
+++ b/uppsrc/Core/Atomic.h
@@ -1,15 +1,4 @@
-#ifdef _MULTITHREADED
-
 typedef std::atomic<int> Atomic;
 
 inline int  AtomicInc(volatile Atomic& t)             { return ++t; }
 inline int  AtomicDec(volatile Atomic& t)             { return --t; }
-
-#else
-
-typedef int Atomic;
-
-inline int  AtomicInc(volatile Atomic& t)             { ++t; return t; }
-inline int  AtomicDec(volatile Atomic& t)             { --t; return t; }
-
-#endif
diff --git a/uppsrc/Core/CoWork.cpp b/uppsrc/Core/CoWork.cpp
index 1c3ceb3fd..b9dff56e6 100644
--- a/uppsrc/Core/CoWork.cpp
+++ b/uppsrc/Core/CoWork.cpp
@@ -2,8 +2,6 @@
 
 namespace Upp {
 
-#ifdef _MULTITHREADED
-
 #define LLOG(x)       // RLOG(x)
 #define LDUMP(x)      // DDUMP(x)
 
@@ -382,6 +380,4 @@ CoWork::~CoWork() noexcept(false)
 	LLOG("~CoWork " << FormatIntHex(this));
 }
 
-#endif
-
 }
diff --git a/uppsrc/Core/CoWork.h b/uppsrc/Core/CoWork.h
index b6cdfabd1..56b2450ef 100644
--- a/uppsrc/Core/CoWork.h
+++ b/uppsrc/Core/CoWork.h
@@ -1,5 +1,3 @@
-#ifdef _MULTITHREADED
-
 class CoWork : NoCopy {
 	struct MJob : Moveable<MJob>, Link<MJob, 2> {
 		Function<void ()> fn;
@@ -223,21 +221,3 @@ Async(Function&& f, Args&&... args)
 	h.Do(f, args...);
 	return pick(h);
 }
-
-#else
-
-class CoWork : NoCopy {
-public:
-	void     Do(Event<>  cb)        { cb(); }
-	CoWork&  operator&(Event<>  cb) { cb(); return *this; }
-	void     Finish()               {}
-	bool     IsFinished()           { return true; }
-
-	static void FinLock()           {}
-
-	static bool IsWorker()          { return false; }
-	static void StartPool(int n)    {}
-	static void ShutdownPool()      {}
-};
-
-#endif
diff --git a/uppsrc/Core/Core.h b/uppsrc/Core/Core.h
index db185c00a..19b36c7a7 100644
--- a/uppsrc/Core/Core.h
+++ b/uppsrc/Core/Core.h
@@ -7,12 +7,10 @@
 #define flagMT // MT is now always on
 #endif
 
-#if defined(flagMT)
-	#define _MULTITHREADED
-	#define MULTITHREADED
-	#ifdef flagDLL
-		#define flagUSEMALLOC
-	#endif
+#define _MULTITHREADED
+#define MULTITHREADED
+#ifdef flagDLL
+	#define flagUSEMALLOC
 #endif
 
 #ifdef flagDLL
diff --git a/uppsrc/Core/SSL/InitExit.cpp b/uppsrc/Core/SSL/InitExit.cpp
index b823614d6..d4788939b 100644
--- a/uppsrc/Core/SSL/InitExit.cpp
+++ b/uppsrc/Core/SSL/InitExit.cpp
@@ -96,7 +96,7 @@ EXITBLOCK
 	ERR_free_strings();
 }
 
-#if defined(_MULTITHREADED) && OPENSSL_VERSION_NUMBER < 0x10100000L
+#if OPENSSL_VERSION_NUMBER < 0x10100000L
 
 static thread_local bool sThreadInit;
 static thread_local void (*sPrevExit)();
diff --git a/uppsrc/Core/TimeDate.cpp b/uppsrc/Core/TimeDate.cpp
index f45408812..3289f2349 100644
--- a/uppsrc/Core/TimeDate.cpp
+++ b/uppsrc/Core/TimeDate.cpp
@@ -74,9 +74,7 @@ static char s_date_format_main[64] = "%2:02d/%3:02d/%1:4d";
 void   SetDateFormat(const char *fmt)
 {
 	strncpy(s_date_format_thread, fmt, 63);
-#ifdef _MULTITHREADED
 	if(Thread::IsMain())
-#endif
 		strncpy(s_date_format_main, fmt, 63);
 }
 
@@ -93,10 +91,8 @@ static char s_date_scan_main[64] = "mdy";
 void   SetDateScan(const char *scan)
 {
 	strncpy(s_date_scan_thread, scan, 63);
-#ifdef _MULTITHREADED
 	if(Thread::IsMain())
-#endif
-		strncpy(s_date_scan_main, scan, 63);	
+		strncpy(s_date_scan_main, scan, 63);
 }
 
 const char *StrToDate(Date& d, const char *s, Date def)
@@ -192,9 +188,7 @@ static char s_date_seps_main[64] = "A/\a .-";
 void   SetDateFilter(const char *seps)
 {
 	strncpy(s_date_seps_thread, seps, 63);
-#ifdef _MULTITHREADED
 	if(Thread::IsMain())
-#endif
 		strncpy(s_date_seps_main, seps, 63);
 }
 
diff --git a/uppsrc/Core/t.cpp b/uppsrc/Core/t.cpp
index 25c066d0b..2904b833f 100644
--- a/uppsrc/Core/t.cpp
+++ b/uppsrc/Core/t.cpp
@@ -250,9 +250,7 @@ void SetCurrentLanguage(int lang)
 		int ii = sLangIndex().FindAdd(lang);
 		sCurrentLangMapPtr = &sLangMap().At(ii);
 		sCurrentSLangMapPtr = &sSLangMap().At(ii);
-	#ifdef _MULTITHREADED
 		if(Thread::IsMain())
-	#endif
 		{
 			main_current_lang = lang;
 			sMainCurrentSLangMapPtr = sCurrentSLangMapPtr;
diff --git a/uppsrc/CtrlCore/CtrlCore.h b/uppsrc/CtrlCore/CtrlCore.h
index a9b17f935..44525174f 100644
--- a/uppsrc/CtrlCore/CtrlCore.h
+++ b/uppsrc/CtrlCore/CtrlCore.h
@@ -52,7 +52,6 @@ namespace Upp {
 
 INITIALIZE(CtrlCore)
 
-#ifdef _MULTITHREADED
 void EnterGuiMutex();
 bool TryEnterGuiMutex();
 void LeaveGuiMutex();
@@ -62,15 +61,6 @@ void EnterGuiMutex(int n);
 
 bool ThreadHasGuiLock();
 int  GetGuiLockLevel();
-#else
-inline void EnterGuiMutex() {}
-inline void LeaveGuiMutex() {}
-inline bool TryEnterGuiMutex() { return true; }
-
-inline int  LeaveGuiMutexAll() { return 0; }
-inline void EnterGuiMutex(int) {}
-inline bool ThreadHasGuiLock() { return true; }
-#endif
 
 struct GuiLock {
 	GuiLock()  { EnterGuiMutex(); }
@@ -1285,10 +1275,8 @@ public:
 
 	static void Call(Function<void ()> cb);
 
-#ifdef _MULTITHREADED
 	static bool IsShutdownThreads()                     { return Thread::IsShutdownThreads(); }
 	static void ShutdownThreads();
-#endif
 	
 	static int64 GetEventId()                           { return eventid; }
 
diff --git a/uppsrc/CtrlCore/CtrlMt.cpp b/uppsrc/CtrlCore/CtrlMt.cpp
index 85365aac5..0b36432e9 100644
--- a/uppsrc/CtrlCore/CtrlMt.cpp
+++ b/uppsrc/CtrlCore/CtrlMt.cpp
@@ -4,8 +4,6 @@
 
 namespace Upp {
 
-#ifdef _MULTITHREADED
-
 static StaticMutex sGLock;
 
 static thread_local int sGLockLevel = 0;
@@ -107,13 +105,4 @@ void Ctrl::ShutdownThreads()
 	Thread::EndShutdownThreads();
 }
 
-#else
-
-void Ctrl::Call(Function<void ()> cb)
-{
-	cb();
-}
-
-#endif
-
 }
diff --git a/uppsrc/CtrlCore/GtkApp.cpp b/uppsrc/CtrlCore/GtkApp.cpp
index dfff39c7f..3bf497a03 100644
--- a/uppsrc/CtrlCore/GtkApp.cpp
+++ b/uppsrc/CtrlCore/GtkApp.cpp
@@ -77,9 +77,7 @@ void InitGtkApp(int argc, char **argv, const char **envptr)
 
 void ExitGtkApp()
 {
-#ifdef _MULTITHREADED
 	LeaveGuiMutex();
-#endif
 }
 
 }
diff --git a/uppsrc/CtrlCore/srcdoc.tpp/GuiMT_en-us.tpp b/uppsrc/CtrlCore/srcdoc.tpp/GuiMT_en-us.tpp
new file mode 100644
index 000000000..035a9e4ed
--- /dev/null
+++ b/uppsrc/CtrlCore/srcdoc.tpp/GuiMT_en-us.tpp
@@ -0,0 +1,41 @@
+topic "GUI programming and multithreading";
+[i448;a25;kKO9;2 $$1,0#37138531426314131252341829483380:class]
+[l288;2 $$2,2#27521748481378242620020725143825:desc]
+[0 $$3,0#96390100711032703541132217272105:end]
+[H6;0 $$4,0#05600065144404261032431302351956:begin]
+[i448;a25;kKO9;2 $$5,0#37138531426314131252341829483370:item]
+[l288;a4;*@5;1 $$6,6#70004532496200323422659154056402:requirement]
+[l288;i1121;b17;O9;~~~.1408;2 $$7,0#10431211400427159095818037425705:param]
+[i448;b42;O9;2 $$8,8#61672508125594000341940100500538:tparam]
+[b42;2 $$9,9#13035079074754324216151401829390:normal]
+[a83;*R6 $$10,0#31310162474203024125188417583966:caption]
+[2 $$0,0#00000000000000000000000000000000:Default]
+[{_}%EN-US 
+[s10; GUI programming and multithreading&]
+[s0; Multithreading in GUI programming model has to follow target 
+platform limitations, where most target platforms have a notion 
+of `"main thread`" and limit GUI actions allowed in non`-main 
+threads.&]
+[s0; &]
+[s0; Everything that is manipulating the status of top`-level windows 
+(TopWindow or popups) and everything related to event loop must 
+run on the main thread. The only non`-const operation allowed 
+to non`-main thread on top`-level windows is Refresh.&]
+[s0; &]
+[s0; Non`-main threads are in general allowed to alter the status 
+of widgets, as long as they serialize access with single global 
+GUI mutex, either with EnterGuiMutex/LeaveGuiMutex or with GuiLock 
+helper guard class (it calls EnterGuiMutex in constructor, LeaveGuiMutex 
+in destructor). GuiLock is reentrant and is optimized for great 
+reentrant performance. It is NOT required to use GuiLock in the 
+even processing methods (like MouseLeft or Key) as U`+`+ locks 
+it in this case itself.&]
+[s0; &]
+[s0; Other means of communication of non`-main threads with main 
+thread is PostCallback, which posts an Event to timer queue for 
+immediate processing, but does not wait for it to finish and 
+Ctrl`::Call, which passes event to main thread to be processed 
+and returns when the event is executed by the main thread. Both 
+of these methods have quite high latency, GuiLock and direct 
+access should be preferred if possible.&]
+[s0; ]]
\ No newline at end of file
diff --git a/uppsrc/CtrlLib/Ch.cpp b/uppsrc/CtrlLib/Ch.cpp
index 7068eada1..599f96a43 100644
--- a/uppsrc/CtrlLib/Ch.cpp
+++ b/uppsrc/CtrlLib/Ch.cpp
@@ -142,7 +142,7 @@ Image MakeElement(Size sz, double radius, const Image& face, double border_width
 Image MakeButton(int radius, const Image& face, double border_width, Color border_color, dword corner)
 {
 	double q = radius + border_width + DPI(16);
-	return MakeElement(Size(q, q), radius, face, border_width, border_color, [&](Painter& w, const Rectf& r) {
+	return MakeElement(Size((int)q, (int)q), radius, face, border_width, border_color, [&](Painter& w, const Rectf& r) {
 		RoundedRect(w, r, radius, radius, corner);
 	});
 }
diff --git a/uppsrc/CtrlLib/FileSel.cpp b/uppsrc/CtrlLib/FileSel.cpp
index 672010586..c44523897 100644
--- a/uppsrc/CtrlLib/FileSel.cpp
+++ b/uppsrc/CtrlLib/FileSel.cpp
@@ -863,8 +863,6 @@ void FileSel::SearchLoad()
 	StartLI();
 }
 
-#ifdef _MULTITHREADED
-
 StaticMutex FileSel::li_mutex;
 void      (*FileSel::li_current)(const String& path, Image& result);
 String      FileSel::li_path;
@@ -961,8 +959,6 @@ void FileSel::StartLI()
 	}
 }
 
-#endif
-
 String TrimDot(String f) {
 	int i = f.Find('.');
 	if(i >= 0 && i == f.GetLength() - 1)
diff --git a/uppsrc/CtrlLib/FileSel.h b/uppsrc/CtrlLib/FileSel.h
index 204e93855..18abfabda 100644
--- a/uppsrc/CtrlLib/FileSel.h
+++ b/uppsrc/CtrlLib/FileSel.h
@@ -224,7 +224,6 @@ protected:
 	Ctrl       *file_ctrl = NULL;
 	int         file_ctrl_cx;
 
-#ifdef _MULTITHREADED
 	static StaticMutex li_mutex;
 	static void      (*li_current)(const String& path, Image& result);
 	static String      li_path;
@@ -238,7 +237,6 @@ protected:
 	void        StartLI();
 	void        DoLI();
 	void        ScheduleLI()                                 { li_tm.KillSet(0, THISBACK(DoLI)); }
-#endif
 
 	void        LoadNet();
 	void        SelectNet();
diff --git a/uppsrc/IconDes/List.cpp b/uppsrc/IconDes/List.cpp
index f99f3381b..fdd31b993 100644
--- a/uppsrc/IconDes/List.cpp
+++ b/uppsrc/IconDes/List.cpp
@@ -282,7 +282,6 @@ struct ImgPreview : Display {
 	}
 };
 
-#ifdef _MULTITHREADED
 static void sLoadImage(const String& path, Image& result)
 {
 	if(findarg(ToLower(GetFileExt(path)), ".png", ".gif", ".jpeg", ".jpg") < 0)
@@ -298,7 +297,6 @@ static void sLoadImage(const String& path, Image& result)
 		return;
 	result = r->GetImage();
 }
-#endif
 
 FileSel& IconDes::ImgFile()
 {
@@ -307,9 +305,7 @@ FileSel& IconDes::ImgFile()
 		sel.Type("Image files", "*.png *.bmp *.jpg *.jpeg *.gif *.ico");
 		sel.AllFilesType();
 		sel.Multi();
-#ifdef _MULTITHREADED
 		sel.WhenIconLazy = sLoadImage;
-#endif
 		sel.Preview(Single<ImgPreview>());
 	}
 	return sel;
diff --git a/uppsrc/plugin/lz4/Compress.cpp b/uppsrc/plugin/lz4/Compress.cpp
index ff8a09cde..12c3158f2 100644
--- a/uppsrc/plugin/lz4/Compress.cpp
+++ b/uppsrc/plugin/lz4/Compress.cpp
@@ -30,14 +30,12 @@ void LZ4CompressStream::Alloc()
 	ptr = ~buffer;
 }
 
-#ifdef _MULTITHREADED
 void LZ4CompressStream::Co(bool b)
 {
 	FlushOut();
 	concurrent = b;
 	Alloc();
 }
-#endif
 
 void LZ4CompressStream::FlushOut()
 {
@@ -51,13 +49,11 @@ void LZ4CompressStream::FlushOut()
 	int   ii = 0;
 	for(byte *s = ~buffer; s < ptr; s += BLOCK_BYTES) {
 		int origsize = min((int)BLOCK_BYTES, int(ptr - s));
-#ifdef _MULTITHREADED
 		if(concurrent)
 			co & [=] {
 				outsz[ii] = LZ4_compress_default((char *)s, (char *)t, origsize, osz);
 			};
 		else
-#endif
 			outsz[ii] = LZ4_compress_default((char *)s, (char *)t, origsize, osz);
 		ii++;
 		t += osz;
diff --git a/uppsrc/plugin/lz4/Decompress.cpp b/uppsrc/plugin/lz4/Decompress.cpp
index cef0fc9be..6431f559a 100644
--- a/uppsrc/plugin/lz4/Decompress.cpp
+++ b/uppsrc/plugin/lz4/Decompress.cpp
@@ -84,9 +84,7 @@ void LZ4DecompressStream::Fetch()
 		return;
 	if(eof)
 		return;
-#ifdef _MULTITHREADED
 	CoWork co;
-#endif
 	bool   error = false;
 	bool last = false;
 	ii = 0;
@@ -120,7 +118,6 @@ void LZ4DecompressStream::Fetch()
 				SetError();
 				return;
 			}
-#ifdef _MULTITHREADED
 			if(concurrent)
 				co & [=, &error] {
 					Workblock& t = wb[i];
@@ -129,9 +126,7 @@ void LZ4DecompressStream::Fetch()
 					if(t.dlen < 0)
 						error = true;
 				};
-			else
-#endif
-			{
+			else {
 				t.dlen = LZ4_decompress_safe(~t.c, ~t.d, t.clen, maxblock);
 				if(t.dlen < 0)
 					error = true;
@@ -140,10 +135,8 @@ void LZ4DecompressStream::Fetch()
 		if(lz4hdr & LZ4F_BLOCKCHECKSUM)
 			in->Get32le(); // just skip it
 	}
-#ifdef _MULTITHREADED
 	if(concurrent)
 		co.Finish();
-#endif
 	if(error)
 		SetError();
 	else {
diff --git a/uppsrc/plugin/lz4/lz4.h b/uppsrc/plugin/lz4/lz4.h
index 78726ed83..16649e291 100644
--- a/uppsrc/plugin/lz4/lz4.h
+++ b/uppsrc/plugin/lz4/lz4.h
@@ -50,9 +50,7 @@ protected:
 	void          FlushOut();
 
 public:
-#ifdef _MULTITHREADED
 	void Co(bool b = true);
-#endif
 	void Open(Stream& out_);
 
 	LZ4CompressStream();
@@ -102,9 +100,7 @@ private:
 public:
 	bool Open(Stream& in);
 
-#ifdef _MULTITHREADED
 	void Co(bool b = true)                                  { concurrent = b; }
-#endif
 
 	LZ4DecompressStream();
 	LZ4DecompressStream(Stream& in) : LZ4DecompressStream() { Open(in); }
@@ -120,7 +116,6 @@ String LZ4Compress(const String& s, Gate<int64, int64> progress = Null);
 String LZ4Decompress(const void *data, int64 len, Gate<int64, int64> progress = Null);
 String LZ4Decompress(const String& s, Gate<int64, int64> progress = Null);
 
-#ifdef _MULTITHREADED
 int64  CoLZ4Compress(Stream& out, Stream& in, Gate<int64, int64> progress = Null);
 int64  CoLZ4Decompress(Stream& out, Stream& in, Gate<int64, int64> progress = Null);
 String CoLZ4Compress(Stream& in, Gate<int64, int64> progress = Null);
@@ -129,7 +124,6 @@ String CoLZ4Compress(const void *data, int64 len, Gate<int64, int64> progress =
 String CoLZ4Compress(const String& s, Gate<int64, int64> progress = Null);
 String CoLZ4Decompress(const void *data, int64 len, Gate<int64, int64> progress = Null);
 String CoLZ4Decompress(const String& s, Gate<int64, int64> progress = Null);
-#endif
 
 bool IsLZ4(Stream& s);
 
diff --git a/uppsrc/plugin/lz4/util.cpp b/uppsrc/plugin/lz4/util.cpp
index 8ea80df59..351cdeabe 100644
--- a/uppsrc/plugin/lz4/util.cpp
+++ b/uppsrc/plugin/lz4/util.cpp
@@ -7,10 +7,8 @@ void sCompressStreamCopy_(Stream& out, Stream& in, Gate<int64, int64> progress,
 static int64 sLZ4Compress(Stream& out, Stream& in, int64 size, Gate<int64, int64> progress, bool co)
 {
 	LZ4CompressStream outs(out);
-#ifdef _MULTITHREADED
 	if(co)
 		outs.Co();
-#endif
 	sCompressStreamCopy_(outs, in, progress, in, size);
 	outs.Close();
 	if(!out.IsError() && !outs.IsError())
@@ -21,10 +19,8 @@ static int64 sLZ4Compress(Stream& out, Stream& in, int64 size, Gate<int64, int64
 static int64 sLZ4Decompress(Stream& out, Stream& in, int64 size, Gate<int64, int64> progress, bool co)
 {
 	LZ4DecompressStream ins(in);
-#ifdef _MULTITHREADED
 	if(co)
 		ins.Co();
-#endif
 	sCompressStreamCopy_(out, ins, progress, in, size);
 	ins.Close();
 	if(!out.IsError() && !ins.IsError())
@@ -76,8 +72,6 @@ String LZ4Decompress(const String& s, Gate<int64, int64> progress)
 	return LZ4Decompress(~s, s.GetLength(), progress);
 }
 
-#ifdef _MULTITHREADED
-
 int64 CoLZ4Compress(Stream& out, Stream& in, Gate<int64, int64> progress)
 {
 	return sLZ4Compress(out, in, in.GetLeft(), progress, true);
@@ -124,6 +118,4 @@ String CoLZ4Decompress(const String& s, Gate<int64, int64> progress)
 	return CoLZ4Decompress(~s, s.GetLength(), progress);
 }
 
-#endif
-
 };
\ No newline at end of file
diff --git a/uppsrc/plugin/zstd/Util.cpp b/uppsrc/plugin/zstd/Util.cpp
index 95a7a92b9..b682ee188 100644
--- a/uppsrc/plugin/zstd/Util.cpp
+++ b/uppsrc/plugin/zstd/Util.cpp
@@ -7,10 +7,8 @@ void sCompressStreamCopy_(Stream& out, Stream& in, Gate<int64, int64> progress,
 static int64 sZstdCompress(Stream& out, Stream& in, int64 size, Gate<int64, int64> progress, bool co)
 {
 	ZstdCompressStream outs(out);
-#ifdef _MULTITHREADED
 	if(co)
 		outs.Co();
-#endif
 	sCompressStreamCopy_(outs, in, progress, in, size);
 	outs.Close();
 	if(!out.IsError() && !outs.IsError())
@@ -21,10 +19,8 @@ static int64 sZstdCompress(Stream& out, Stream& in, int64 size, Gate<int64, int6
 static int64 sZstdDecompress(Stream& out, Stream& in, int64 size, Gate<int64, int64> progress, bool co)
 {
 	ZstdDecompressStream ins(in);
-#ifdef _MULTITHREADED
 	if(co)
 		ins.Co();
-#endif
 	sCompressStreamCopy_(out, ins, progress, in, size);
 	ins.Close();
 	if(!out.IsError() && !ins.IsError())
@@ -66,8 +62,6 @@ String ZstdDecompress(const String& s, Gate<int64, int64> progress)
 	return ZstdDecompress(~s, s.GetLength(), progress);
 }
 
-#ifdef _MULTITHREADED
-
 int64 CoZstdCompress(Stream& out, Stream& in, Gate<int64, int64> progress)
 {
 	return sZstdCompress(out, in, in.GetLeft(), progress, true);
@@ -102,6 +96,4 @@ String CoZstdDecompress(const String& s, Gate<int64, int64> progress)
 	return CoZstdDecompress(~s, s.GetLength(), progress);
 }
 
-#endif
-
 };
\ No newline at end of file
diff --git a/uppsrc/plugin/zstd/zstd.h b/uppsrc/plugin/zstd/zstd.h
index dc4efd89a..e7d5ce6d4 100644
--- a/uppsrc/plugin/zstd/zstd.h
+++ b/uppsrc/plugin/zstd/zstd.h
@@ -34,9 +34,7 @@ protected:
 	void          FlushOut();
 
 public:
-#ifdef _MULTITHREADED
 	void Co(bool b = true);
-#endif
 	void Open(Stream& out, int level = 1);
 
 	ZstdCompressStream();
@@ -92,10 +90,7 @@ private:
 
 public:	
 	bool Open(Stream& in);
-
-#ifdef _MULTITHREADED
 	void Co(bool b = true)                                    { concurrent = b; }
-#endif
 
 	ZstdDecompressStream();
 	ZstdDecompressStream(Stream& in) : ZstdDecompressStream() { Open(in); }
@@ -109,14 +104,12 @@ String ZstdCompress(const String& s, Gate<int64, int64> progress = Null);
 String ZstdDecompress(const void *data, int64 len, Gate<int64, int64> progress = Null);
 String ZstdDecompress(const String& s, Gate<int64, int64> progress = Null);
 
-#ifdef _MULTITHREADED
 int64 CoZstdCompress(Stream& out, Stream& in, Gate<int64, int64> progress = Null);
 int64 CoZstdDecompress(Stream& out, Stream& in, Gate<int64, int64> progress = Null);
 String CoZstdCompress(const void *data, int64 len, Gate<int64, int64> progress = Null);
 String CoZstdCompress(const String& s, Gate<int64, int64> progress = Null);
 String CoZstdDecompress(const void *data, int64 len, Gate<int64, int64> progress = Null);
 String CoZstdDecompress(const String& s, Gate<int64, int64> progress = Null);
-#endif
 
 bool IsZstd(Stream& s);