diff --git a/pttyhandler.cpp b/pttyhandler.cpp
index b9205b7..0bdc79a 100644
--- a/pttyhandler.cpp
+++ b/pttyhandler.cpp
@@ -155,7 +155,7 @@ void pttyHandler::sendDataOut(const QByteArray& writeData)
 
     qint64 bytesWritten=0;
 
-    if (inPortData[2] != (char)0xE1 && inPortData[3] != (char)0xE1) {
+    if ((unsigned char)inPortData[2] != 0xE1 && (unsigned char)inPortData[3] != 0xE1) {
         bytesWritten = port->write(writeData);
         if (bytesWritten != writeData.length()) {
             qDebug(logSerial()) << "bytesWritten: " << bytesWritten << " length of byte array: " << writeData.length()\