diff --git a/lib/cpp/src/transport/TTransportUtils.h b/lib/cpp/src/transport/TTransportUtils.h
index 9499acd..518969f 100644
--- a/lib/cpp/src/transport/TTransportUtils.h
+++ b/lib/cpp/src/transport/TTransportUtils.h
@@ -319,7 +319,7 @@
     if (buffer_ == NULL) {
       return "";
     }
-    return std::string((char*)buffer_, (std::string::size_type)bufferSize_);
+    return std::string((char*)buffer_, (std::string::size_type)wPos_);
   }
 
   void appendBufferToString(std::string& str) {