diff --git a/src/GUI.cpp b/src/GUI.cpp
index 57587735a..dbe273262 100644
--- a/src/GUI.cpp
+++ b/src/GUI.cpp
@@ -85,7 +85,13 @@ using namespace libtorrent;
 GUI::GUI(QWidget *parent, QStringList torrentCmdLine) : QMainWindow(parent), displaySpeedInTitle(false), force_exit(false) {
   setupUi(this);
 
-  setWindowTitle(tr("qBittorrent %1", "e.g: qBittorrent v0.x").arg(QString::fromUtf8(VERSION)));
+  setWindowTitle(tr("qBittorrent %1", "e.g: qBittorrent v0.x").arg(QString::fromUtf8(VERSION))
+#if defined(Q_WS_WIN)
+  +" [Windows]"
+#elif defined(Q_WS_MAC)
+  +" [Mac OS X]"
+#endif
+  );
   // Setting icons
   this->setWindowIcon(QIcon(QString::fromUtf8(":/Icons/skin/qbittorrent32.png")));
   actionOpen->setIcon(QIcon(QString::fromUtf8(":/Icons/skin/open.png")));