diff --git a/pyqtgraph/flowchart/Flowchart.py b/pyqtgraph/flowchart/Flowchart.py
index b623f5c..0af0964 100644
--- a/pyqtgraph/flowchart/Flowchart.py
+++ b/pyqtgraph/flowchart/Flowchart.py
@@ -1,4 +1,6 @@
 # -*- coding: utf-8 -*-
+import os
+
 from ..Qt import QtCore, QtGui, USE_PYSIDE, USE_PYQT5
 from .Node import *
 from ..pgcollections import OrderedDict
diff --git a/tools/plottingtool.py b/tools/plottingtool.py
index 6f917da..5d491fe 100644
--- a/tools/plottingtool.py
+++ b/tools/plottingtool.py
@@ -22,6 +22,7 @@
 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 #
 #---------------------------------------------------------------------
+import os
 
 from qgis.core import *
 from qgis.gui import *