diff --git a/src/RS232_win.c b/src/RS232_win.c
--- a/src/RS232_win.c
+++ b/src/RS232_win.c
@@ -326,7 +326,7 @@ int rs232availablebytes(rs232port_t fd)
 {
     DWORD dwErrorFlags;
     COMSTAT ComStat;
-    ClearCommError(m_hIDComDev, &dwErrorFlags, &ComStat);
+    ClearCommError(fd, &dwErrorFlags, &ComStat);
     return((int)ComStat.cbInQue);
 }