diff --git a/src/io/piconnection.cpp b/src/io/piconnection.cpp
index 904dfb2a..58c79de9 100755
--- a/src/io/piconnection.cpp
+++ b/src/io/piconnection.cpp
@@ -861,6 +861,7 @@ int PIConnection::write(PIIODevice * dev, const PIByteArray & data) {
 		piCoutObj << "Null Device!";
 		return -1;
 	}
+	if (!dev->isOpened()) return -1;
 	if (!dev->canWrite()) {
 		piCoutObj << "Device \"" << dev->constructFullPath() << "\" can`t write!";
 		return -1;