diff --git a/README.md b/README.md
--- a/README.md
+++ b/README.md
@@ -5,3 +5,7 @@ Small and simple software for plotting d
 - Qt 5, including serialport module
 - qwt 6.1
 - libudev-dev (required for QSerialPort)
+
+# Known Issues
+- Port error 13 happens when closing. This is a Qt issue. It's known
+  to not happen Qt 5.4.1 .