diff --git a/Orange/widgets/unsupervised/owhierarchicalclustering.py b/Orange/widgets/unsupervised/owhierarchicalclustering.py
index f6cc9dcdfb6..6a30d2fade6 100644
--- a/Orange/widgets/unsupervised/owhierarchicalclustering.py
+++ b/Orange/widgets/unsupervised/owhierarchicalclustering.py
@@ -7,10 +7,10 @@
 import numpy as np
 
 from AnyQt.QtWidgets import (
-    QGraphicsWidget, QGraphicsObject, QGraphicsScene, QGridLayout, QSizePolicy,
+    QGraphicsWidget, QGraphicsScene, QGridLayout, QSizePolicy,
     QAction, QComboBox, QGraphicsGridLayout, QGraphicsSceneMouseEvent
 )
-from AnyQt.QtGui import QColor, QPen, QFont, QKeySequence
+from AnyQt.QtGui import QPen, QFont, QKeySequence, QPainterPath
 from AnyQt.QtCore import Qt, QSizeF, QPointF, QRectF, QLineF, QEvent
 from AnyQt.QtCore import pyqtSignal as Signal, pyqtSlot as Slot
 
@@ -891,7 +891,7 @@ def mouseReleaseEvent(self, event):
         event.accept()
 
 
-class SliderLine(QGraphicsObject):
+class SliderLine(QGraphicsWidget):
     """A movable slider line."""
     valueChanged = Signal(float)
 
@@ -907,14 +907,10 @@ def __init__(self, parent=None, orientation=Qt.Vertical, value=0.0,
         self._length = length
         self._min = 0.0
         self._max = 1.0
-        self._line = QLineF()  # type: Optional[QLineF]
-        self._pen = QPen()
+        self._line: Optional[QLineF] = QLineF()
+        self._pen: Optional[QPen] = None
         super().__init__(parent, **kwargs)
-
         self.setAcceptedMouseButtons(Qt.LeftButton)
-        self.setPen(make_pen(brush=QColor(50, 50, 50), width=1, cosmetic=False,
-                             style=Qt.DashLine))
-
         if self._orientation == Qt.Vertical:
             self.setCursor(Qt.SizeVerCursor)
         else:
@@ -929,7 +925,10 @@ def setPen(self, pen: Union[QPen, Qt.GlobalColor, Qt.PenStyle]) -> None:
             self.update()
 
     def pen(self) -> QPen:
-        return QPen(self._pen)
+        if self._pen is None:
+            return QPen(self.palette().text(), 1.0, Qt.DashLine)
+        else:
+            return QPen(self._pen)
 
     def setValue(self, value: float):
         value = min(max(value, self._min), self._max)
@@ -991,6 +990,11 @@ def mouseReleaseEvent(self, event: QGraphicsSceneMouseEvent) -> None:
         self.lineReleased.emit()
         event.accept()
 
+    def shape(self) -> QPainterPath:
+        path = QPainterPath()
+        path.addRect(self.boundingRect())
+        return path
+
     def boundingRect(self) -> QRectF:
         if self._line is None:
             if self._orientation == Qt.Vertical: