1 files changed, 2 insertions, 2 deletions
diff --git a/src/serialport/qserialport_win.cpp b/src/serialport/qserialport_win.cpp
index d6a1d13..7ae40d9 100644
--- a/src/serialport/qserialport_win.cpp
+++ b/src/serialport/qserialport_win.cpp
@@ -537,11 +537,11 @@ bool QSerialPortPrivate::startAsyncRead()
     if (readStarted)
         return true;
 
-    DWORD bytesToRead = QSERIALPORT_BUFFERSIZE;
+    qint64 bytesToRead = QSERIALPORT_BUFFERSIZE;
 
     if (readBufferMaxSize && bytesToRead > (readBufferMaxSize - buffer.size())) {
         bytesToRead = readBufferMaxSize - buffer.size();
-        if (bytesToRead == 0) {
+        if (bytesToRead <= 0) {
             // Buffer is full. User must read data from the buffer
             // before we can read more from the port.
             return false;