diff --git a/Orange/widgets/utils/overlay.py b/Orange/widgets/utils/overlay.py
index c174c874ada..75faaabde39 100644
--- a/Orange/widgets/utils/overlay.py
+++ b/Orange/widgets/utils/overlay.py
@@ -18,7 +18,7 @@
     QWidget, QPixmap, QStyleOption, QPainter
 )
 from PyQt4.QtCore import Qt, QSize, QRect, QPoint, QEvent, QTimer
-from PyQt4.QtCore import pyqtSignal as Signal
+from PyQt4.QtCore import pyqtSignal as Signal, pyqtSlot as Slot
 
 
 class OverlayWidget(QWidget):
@@ -172,6 +172,7 @@ def getsize(hint, minimum, maximum, policy):
         geom = QRect(QPoint(x, y), size)
         self.setGeometry(geom)
 
+    @Slot()
     def __on_destroyed(self):
         self.__widget = None
         if self.isVisible():