diff --git a/UMP.h b/UMP.h
index 17a1e97..2be9447 100644
--- a/UMP.h
+++ b/UMP.h
@@ -48,6 +48,7 @@ public:
 
 private:
 	CSerialController m_serial;
+	bool              m_open;
 	unsigned char*    m_buffer;
 	unsigned int      m_length;
 	unsigned int      m_offset;