diff --git a/rdkit/Chem/Draw/UnitTestSimilarityMaps.py b/rdkit/Chem/Draw/UnitTestSimilarityMaps.py
index 3b85450..9f39c92 100755
--- a/rdkit/Chem/Draw/UnitTestSimilarityMaps.py
+++ b/rdkit/Chem/Draw/UnitTestSimilarityMaps.py
@@ -98,6 +98,7 @@ class TestCase(unittest.TestCase):
 if __name__ == '__main__':
   try:
     import matplotlib
+    matplotlib.use('cairo')
     from rdkit.Chem.Draw.mplCanvas import Canvas
   except ImportError:
     pass