diff --git a/unittest/python/test_eigen_ref.py b/unittest/python/test_eigen_ref.py
index 0434ccacd48fc0bc1657f56c0243345b1348b108..5b6282e1fb2d4e8bf0f8c23ea9f85ad2fb3ccd0f 100644
--- a/unittest/python/test_eigen_ref.py
+++ b/unittest/python/test_eigen_ref.py
@@ -49,7 +49,7 @@ def test(mat):
 
     class ModifyBlockImpl(modify_block):
         def __init__(self):
-            super().__init__()
+            super(ModifyBlockImpl, self).__init__()
 
         def call(self, mat):
             n, m = mat.shape