diff --git a/README.md b/README.md
index 1dfb87a032e8720782d30dc1db0aee0b00f564d8..79fcb6dbefdc0e6d627165f34aa6ff46dd43babd 100644
--- a/README.md
+++ b/README.md
@@ -30,7 +30,7 @@ A simple example on how to use this package:
 
 ```python
 import numpy as np
-from csst_proto import flip_image, print_data
+from csst_proto.top_level_interface import flip_image, read_test_image
 from astropy.io import fits
 
 # read an L0 image
diff --git a/csst_proto/flip_image.py b/csst_proto/flip_image.py
index 7f7aa41f2be483f65a80e44bc924549b15df4977..b8cb64389be7e2d242d7e7d5f7d1dd478636fd36 100644
--- a/csst_proto/flip_image.py
+++ b/csst_proto/flip_image.py
@@ -30,4 +30,4 @@ def flip_image(img: np.ndarray):
 def read_test_image():
     """ read test image """
     fp_img = PACKAGE_PATH + "/data/test_image.txt"
-    return np.loadtxt(fp_img)
+    return np.loadtxt(fp_img, dtype=int)