diff --git a/tests/python_tests/png_encoding_test.py b/tests/python_tests/png_encoding_test.py
index 05ae603fe..fc571ba28 100644
--- a/tests/python_tests/png_encoding_test.py
+++ b/tests/python_tests/png_encoding_test.py
@@ -130,7 +130,7 @@ def test_transparency_levels_aerial():
 
     im_in = mapnik.Image.open('./images/support/transparency/aerial_rgb.png')
     eq_(len(im.tostring('png')),len(im_in.tostring('png')))
-    #eq_(len(im.tostring('png:t=0')),len(im_in.tostring('png:t=0')))
+    eq_(len(im.tostring('png:t=0')),len(im_in.tostring('png:t=0')))
 
 
 if __name__ == "__main__":