diff --git a/tests/nightly/model_backwards_compatibility_check/common.py b/tests/nightly/model_backwards_compatibility_check/common.py
index d8ffca25a3f3..cbdc61948b88 100644
--- a/tests/nightly/model_backwards_compatibility_check/common.py
+++ b/tests/nightly/model_backwards_compatibility_check/common.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Licensed to the Apache Software Foundation (ASF) under one
 # or more contributor license agreements.  See the NOTICE file
@@ -29,12 +29,9 @@
 import re
 from mxnet.test_utils import assert_almost_equal
 
-try:
-    cmp             # Python 2
-except NameError:
-    # See: https://docs.python.org/3.0/whatsnew/3.0.html#ordering-comparisons
-    def cmp(x, y):  # Python 3
-        return (x > y) - (x < y)
+
+def cmp(x, y):  # Python 3
+    return (x > y) - (x < y)
 
 # Set fixed random seeds.
 mx.random.seed(7)
diff --git a/tests/nightly/model_backwards_compatibility_check/model_backward_compat_checker.sh b/tests/nightly/model_backwards_compatibility_check/model_backward_compat_checker.sh
index ba53146c3225..9980dff9da94 100755
--- a/tests/nightly/model_backwards_compatibility_check/model_backward_compat_checker.sh
+++ b/tests/nightly/model_backwards_compatibility_check/model_backward_compat_checker.sh
@@ -28,4 +28,4 @@ echo `pwd`
 
 echo '=========================='
 export MXNET_ENFORCE_DETERMINISM=1
-python model_backwards_compat_inference.py
+python3 model_backwards_compat_inference.py
diff --git a/tests/nightly/model_backwards_compatibility_check/model_backwards_compat_inference.py b/tests/nightly/model_backwards_compatibility_check/model_backwards_compat_inference.py
index 5d63e7e9bca3..ee966dd291f1 100644
--- a/tests/nightly/model_backwards_compatibility_check/model_backwards_compat_inference.py
+++ b/tests/nightly/model_backwards_compatibility_check/model_backwards_compat_inference.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Licensed to the Apache Software Foundation (ASF) under one
 # or more contributor license agreements.  See the NOTICE file
diff --git a/tests/nightly/model_backwards_compatibility_check/model_backwards_compat_train.py b/tests/nightly/model_backwards_compatibility_check/model_backwards_compat_train.py
index 289d47c705db..f454eb7d3393 100644
--- a/tests/nightly/model_backwards_compatibility_check/model_backwards_compat_train.py
+++ b/tests/nightly/model_backwards_compatibility_check/model_backwards_compat_train.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Licensed to the Apache Software Foundation (ASF) under one
 # or more contributor license agreements.  See the NOTICE file