diff --git a/tests/test_flip_image.py b/tests/test_flip_image.py
index c4d2cb4e16d80d851e6cfc8bcbc85b7148e7f847..7d7ca5cb6ff8b2b9a1ffaa36ea75673dd77573e2 100644
--- a/tests/test_flip_image.py
+++ b/tests/test_flip_image.py
@@ -20,13 +20,13 @@ class FlipImageTestCase(unittest.TestCase):
 
     def test_flip_image_on_server(self):
         """test flip image on server"""
-        image_input = np.load(
+        image_input = np.loadtxt(
             os.path.join(
                 os.environ["UNIT_TEST_DATA_ROOT"],
                 "csst_proto/test_flip/input/image.txt",
             )
         )
-        image_answer = np.load(
+        image_answer = np.loadtxt(
             os.path.join(
                 os.environ["UNIT_TEST_DATA_ROOT"],
                 "csst_proto/test_flip/answer/flipped_image.txt",