diff --git a/src/binarystreamreader.cpp b/src/binarystreamreader.cpp
--- a/src/binarystreamreader.cpp
+++ b/src/binarystreamreader.cpp
@@ -1,5 +1,5 @@
 /*
-  Copyright © 2017 Hasan Yavuz Özderya
+  Copyright © 2018 Hasan Yavuz Özderya
 
   This file is part of serialplot.
 
@@ -145,7 +145,7 @@ void BinaryStreamReader::onDataReady()
     {
         _device->read(sampleSize);
         skipSampleRequested = false;
-        bytesAvailable--;
+        bytesAvailable -= sampleSize;
     }
 
     if (bytesAvailable < packageSize) return;