diff --git a/mt/CThread.cpp b/mt/CThread.cpp
index 9df33fb9..f67573fb 100644
--- a/mt/CThread.cpp
+++ b/mt/CThread.cpp
@@ -117,3 +117,18 @@ bool					CThread::operator!=(const CThread& thread) const
 {
 	return (m_rep != thread.m_rep);
 }
+
+
+//
+// CThreadMaskCancel
+//
+
+CThreadMaskCancel::CThreadMaskCancel() : m_old(CThread::enableCancel(false))
+{
+	// do nothing
+}
+
+CThreadMaskCancel::~CThreadMaskCancel()
+{
+	CThread::enableCancel(m_old);
+}
diff --git a/mt/CThread.h b/mt/CThread.h
index 982a1912..b6ebe1e3 100644
--- a/mt/CThread.h
+++ b/mt/CThread.h
@@ -125,8 +125,8 @@ private:
 // disables cancellation in the c'tor and enables it in the d'tor.
 class CThreadMaskCancel {
 public:
-	CThreadMaskCancel() : m_old(CThread::enableCancel(false)) { }
-	~CThreadMaskCancel() { CThread::enableCancel(m_old); }
+	CThreadMaskCancel();
+	~CThreadMaskCancel();
 
 private:
 	bool				m_old;
diff --git a/mt/CThreadRep.cpp b/mt/CThreadRep.cpp
index 4b2de42a..8b48f6b8 100644
--- a/mt/CThreadRep.cpp
+++ b/mt/CThreadRep.cpp
@@ -534,10 +534,21 @@ bool					CThreadRep::wait(CThreadRep* target, double timeout)
 
 void					CThreadRep::setPriority(int n)
 {
+	DWORD pClass = NORMAL_PRIORITY_CLASS;
 	if (n < 0) {
 		switch (-n) {
 		case 1:  n = THREAD_PRIORITY_ABOVE_NORMAL; break;
-		default: n = THREAD_PRIORITY_HIGHEST; break;
+		case 2:  n = THREAD_PRIORITY_HIGHEST; break;
+		default:
+			pClass = HIGH_PRIORITY_CLASS;
+			switch (-n - 3) {
+			case 0:  n = THREAD_PRIORITY_LOWEST; break;
+			case 1:  n = THREAD_PRIORITY_BELOW_NORMAL; break;
+			case 2:  n = THREAD_PRIORITY_NORMAL; break;
+			case 3:  n = THREAD_PRIORITY_ABOVE_NORMAL; break;
+			default: n = THREAD_PRIORITY_HIGHEST; break;
+			}
+			break;
 		}
 	}
 	else {
@@ -548,6 +559,7 @@ void					CThreadRep::setPriority(int n)
 		default: n = THREAD_PRIORITY_IDLE; break;
 		}
 	}
+	SetPriorityClass(m_thread, pClass);
 	SetThreadPriority(m_thread, n);
 }