diff --git a/pyqtgraph/widgets/TreeWidget.py b/pyqtgraph/widgets/TreeWidget.py
index 8c55ae2f..4540915f 100644
--- a/pyqtgraph/widgets/TreeWidget.py
+++ b/pyqtgraph/widgets/TreeWidget.py
@@ -132,7 +132,7 @@ class TreeWidget(QtGui.QTreeWidget):
     
     def listAllItems(self, item=None):
         items = []
-        if item != None:
+        if item is not None:
             items.append(item)
         else:
             item = self.invisibleRootItem()