diff --git a/lib/arch/CArchMultithreadWindows.cpp b/lib/arch/CArchMultithreadWindows.cpp
index ba2fef6d..e9101515 100644
--- a/lib/arch/CArchMultithreadWindows.cpp
+++ b/lib/arch/CArchMultithreadWindows.cpp
@@ -388,14 +388,17 @@ CArchMultithreadWindows::setPriorityOfThread(CArchThread thread, int n)
 
 	assert(thread != NULL);
 
-	size_t index = s_pBase - n;
-	if (index < 0) {
+	size_t index;
+	if (s_pBase < n) {
 		// lowest priority
 		index = 0;
 	}
-	else if (index > s_pMax) {
-		// highest priority
-		index = s_pMax;
+	else {
+		index = s_pBase - n;
+		if (index > s_pMax) {
+			// highest priority
+			index = s_pMax;
+		}
 	}
 	SetPriorityClass(thread->m_thread, s_pClass[index].m_class);
 	SetThreadPriority(thread->m_thread, s_pClass[index].m_level);
diff --git a/lib/synergy/CPrimaryScreen.cpp b/lib/synergy/CPrimaryScreen.cpp
index 19bbc8b2..320733f0 100644
--- a/lib/synergy/CPrimaryScreen.cpp
+++ b/lib/synergy/CPrimaryScreen.cpp
@@ -40,7 +40,7 @@ void
 CPrimaryScreen::mainLoop()
 {
 	// change our priority
-	CThread::getCurrentThread().setPriority(-13);
+	CThread::getCurrentThread().setPriority(-14);
 
 	// run event loop
 	try {
diff --git a/lib/synergy/CSecondaryScreen.cpp b/lib/synergy/CSecondaryScreen.cpp
index c3df69bb..e7e72e70 100644
--- a/lib/synergy/CSecondaryScreen.cpp
+++ b/lib/synergy/CSecondaryScreen.cpp
@@ -40,7 +40,7 @@ void
 CSecondaryScreen::mainLoop()
 {
 	// change our priority
-	CThread::getCurrentThread().setPriority(-13);
+	CThread::getCurrentThread().setPriority(-14);
 
 	// run event loop
 	try {