diff --git a/mt/CTimerThread.cpp b/mt/CTimerThread.cpp
index 0a3e8542..786ed8df 100644
--- a/mt/CTimerThread.cpp
+++ b/mt/CTimerThread.cpp
@@ -10,20 +10,27 @@
 
 CTimerThread::CTimerThread(double timeout) : m_timeout(timeout)
 {
-	assert(m_timeout > 0.0);
-	m_callingThread = new CThread(CThread::getCurrentThread());
-	m_timingThread  = new CThread(new TMethodJob<CTimerThread>(
+	if (m_timeout >= 0.0) {
+		m_callingThread = new CThread(CThread::getCurrentThread());
+		m_timingThread  = new CThread(new TMethodJob<CTimerThread>(
 								this, &CTimerThread::timer));
+	}
+	else {
+		m_callingThread = NULL;
+		m_timingThread  = NULL;
+	}
 }
 
 CTimerThread::~CTimerThread()
 {
-	log((CLOG_DEBUG1 "cancelling timeout"));
-	m_timingThread->cancel();
-	m_timingThread->wait();
-	log((CLOG_DEBUG1 "cancelled timeout"));
-	delete m_timingThread;
-	delete m_callingThread;
+	if (m_timingThread != NULL) {
+		log((CLOG_DEBUG1 "cancelling timeout"));
+		m_timingThread->cancel();
+		m_timingThread->wait();
+		log((CLOG_DEBUG1 "cancelled timeout"));
+		delete m_timingThread;
+		delete m_callingThread;
+	}
 }
 
 void					CTimerThread::timer(void*)
diff --git a/mt/CTimerThread.h b/mt/CTimerThread.h
index 817642d3..118fde1d 100644
--- a/mt/CTimerThread.h
+++ b/mt/CTimerThread.h
@@ -7,6 +7,9 @@ class CThread;
 
 class CTimerThread {
 public:
+	// cancels the calling thread after timeout seconds unless destroyed
+	// before then.  if timeout is less than zero then it never times
+	// out and is a no-op.
 	CTimerThread(double timeout);
 	~CTimerThread();