diff --git a/pyqtgraph/widgets/GroupBox.py b/pyqtgraph/widgets/GroupBox.py
index 14a8dab5..43250115 100644
--- a/pyqtgraph/widgets/GroupBox.py
+++ b/pyqtgraph/widgets/GroupBox.py
@@ -1,5 +1,7 @@
 from ..Qt import QtGui, QtCore
 from .PathButton import PathButton
+from ..python2_3 import basestring
+
 
 class GroupBox(QtGui.QGroupBox):
     """Subclass of QGroupBox that implements collapse handle.