diff --git a/winpr/libwinpr/comm/comm.h b/winpr/libwinpr/comm/comm.h
index b382cdfa7..ac149133e 100644
--- a/winpr/libwinpr/comm/comm.h
+++ b/winpr/libwinpr/comm/comm.h
@@ -74,8 +74,8 @@ typedef struct winpr_comm WINPR_COMM;
 void _comm_setRemoteSerialDriver(HANDLE hComm, REMOTE_SERIAL_DRIVER_ID);
 
 /* TMP: TODO: move all specific defines and types here? at least SERIAL_EV_* */
-#define SERIAL_EV_FREERDP_STOP     0x4000 /* bit unused by SERIAL_EV_* */
-#define SERIAL_EV_FREERDP_CLOSING  0x8000 /* bit unused by SERIAL_EV_* */
+#define SERIAL_EV_FREERDP_WAITING	0x4000 /* bit unused by SERIAL_EV_* */
+#define SERIAL_EV_FREERDP_STOP     	0x8000 /* bit unused by SERIAL_EV_* */
 
 
 #endif /* _WIN32 */
diff --git a/winpr/libwinpr/comm/comm_serial_sys.c b/winpr/libwinpr/comm/comm_serial_sys.c
index 678aa74ee..4df984036 100644
--- a/winpr/libwinpr/comm/comm_serial_sys.c
+++ b/winpr/libwinpr/comm/comm_serial_sys.c
@@ -1013,14 +1013,27 @@ static BOOL _set_wait_mask(WINPR_COMM *pComm, const ULONG *pWaitMask)
 {
 	ULONG possibleMask;
 
+
+	/* Stops pending IOCTL_SERIAL_WAIT_ON_MASK
+	 * http://msdn.microsoft.com/en-us/library/ff546805%28v=vs.85%29.aspx
+	 */
+
+	if (pComm->PendingEvents & SERIAL_EV_FREERDP_WAITING)
+	{
+		/* FIXME: any doubt on reading PendingEvents out of a critical section? */
+
+		EnterCriticalSection(&pComm->EventsLock);
+		pComm->PendingEvents |= SERIAL_EV_FREERDP_STOP;
+		LeaveCriticalSection(&pComm->EventsLock);
+
+		/* waiting the end of the pending _wait_on_mask() */
+		while (pComm->PendingEvents & SERIAL_EV_FREERDP_WAITING)
+			Sleep(10); /* 10ms */
+	}
+
 	/* NB: ensure to leave the critical section before to return */
 	EnterCriticalSection(&pComm->EventsLock);
 
-	if (pComm->PendingEvents & SERIAL_EV_FREERDP_CLOSING)
-	{
-		return TRUE; /* returns without complaining */
-	}
-
 	if (*pWaitMask == 0)
 	{
 		/* clearing pending events */
@@ -1037,11 +1050,6 @@ static BOOL _set_wait_mask(WINPR_COMM *pComm, const ULONG *pWaitMask)
 		pComm->PendingEvents = 0;
 	}
 
-	/* Stops pending IOCTL_SERIAL_WAIT_ON_MASK
-	 * http://msdn.microsoft.com/en-us/library/ff546805%28v=vs.85%29.aspx
-	 */
-	pComm->PendingEvents |= SERIAL_EV_FREERDP_STOP;
-
 	possibleMask = *pWaitMask & _SERIAL_SYS_SUPPORTED_EV_MASK;
 
 	if (possibleMask != *pWaitMask)
@@ -1170,11 +1178,6 @@ static BOOL _get_commstatus(WINPR_COMM *pComm, SERIAL_STATUS *pCommstatus)
 	/* NB: ensure to leave the critical section before to return */
 	EnterCriticalSection(&pComm->EventsLock);
 
-	if (pComm->PendingEvents & SERIAL_EV_FREERDP_CLOSING)
-	{
-		return TRUE; /* returns without complaining */
-	}
-
 	ZeroMemory(pCommstatus, sizeof(SERIAL_STATUS));
 
 	ZeroMemory(&currentCounters, sizeof(struct serial_icounter_struct));
@@ -1338,25 +1341,25 @@ static BOOL _wait_on_mask(WINPR_COMM *pComm, ULONG *pOutputMask)
 {
 	assert(*pOutputMask == 0);
 
-	/* UGLY: removes the STOP bit set by an initial _set_wait_mask() */
-	pComm->PendingEvents &= ~SERIAL_EV_FREERDP_STOP;
+	EnterCriticalSection(&pComm->EventsLock);
+	pComm->PendingEvents |= SERIAL_EV_FREERDP_WAITING;
+	LeaveCriticalSection(&pComm->EventsLock);
+
 
 	while (TRUE)
 	{
 		/* NB: EventsLock also used by _refresh_PendingEvents() */
 		if (!_refresh_PendingEvents(pComm))
 		{
+			EnterCriticalSection(&pComm->EventsLock);
+			pComm->PendingEvents &= ~SERIAL_EV_FREERDP_WAITING;
+			LeaveCriticalSection(&pComm->EventsLock);
 			return FALSE;
 		}
 
 		/* NB: ensure to leave the critical section before to return */
 		EnterCriticalSection(&pComm->EventsLock);
 		
-		if (pComm->PendingEvents & SERIAL_EV_FREERDP_CLOSING)
-		{
-			return TRUE; /* returns without complaining */
-		}
-
 		if (pComm->PendingEvents & SERIAL_EV_FREERDP_STOP)
 		{
 			pComm->PendingEvents &= ~SERIAL_EV_FREERDP_STOP;
@@ -1368,6 +1371,7 @@ static BOOL _wait_on_mask(WINPR_COMM *pComm, ULONG *pOutputMask)
 			 */
 			assert(*pOutputMask == 0);
 
+			pComm->PendingEvents &= ~SERIAL_EV_FREERDP_WAITING;
 			LeaveCriticalSection(&pComm->EventsLock);
 			return TRUE;
 		}
@@ -1391,6 +1395,10 @@ static BOOL _wait_on_mask(WINPR_COMM *pComm, ULONG *pOutputMask)
 		if (*pOutputMask != 0)
 		{
 			/* at least an event occurred */
+
+			EnterCriticalSection(&pComm->EventsLock);
+			pComm->PendingEvents &= ~SERIAL_EV_FREERDP_WAITING;
+			LeaveCriticalSection(&pComm->EventsLock);
 			return TRUE;
 		}
 
@@ -1407,6 +1415,9 @@ static BOOL _wait_on_mask(WINPR_COMM *pComm, ULONG *pOutputMask)
 	}
 
 	DEBUG_WARN("_wait_on_mask, unexpected return, WaitEventMask=0X%lX", pComm->WaitEventMask);
+	EnterCriticalSection(&pComm->EventsLock);
+	pComm->PendingEvents &= ~SERIAL_EV_FREERDP_WAITING;
+	LeaveCriticalSection(&pComm->EventsLock);
 	assert(FALSE);
 	return FALSE;
 }
diff --git a/winpr/libwinpr/handle/handle.c b/winpr/libwinpr/handle/handle.c
index 4d777d265..e7ada73ba 100644
--- a/winpr/libwinpr/handle/handle.c
+++ b/winpr/libwinpr/handle/handle.c
@@ -208,7 +208,7 @@ BOOL CloseHandle(HANDLE hObject)
 		 * SERIAL_EV_FREERDP_STOP anyway. Remove this code if
 		 * you think otherwise. */
 		EnterCriticalSection(&comm->EventsLock);
-		comm->PendingEvents |= SERIAL_EV_FREERDP_CLOSING;
+		comm->PendingEvents |= SERIAL_EV_FREERDP_STOP;
 		LeaveCriticalSection(&comm->EventsLock);
 
 		DeleteCriticalSection(&comm->EventsLock);