diff --git a/pymispgalaxies/__init__.py b/pymispgalaxies/__init__.py
index d6ca4a5..1f820e6 100644
--- a/pymispgalaxies/__init__.py
+++ b/pymispgalaxies/__init__.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 from .api import Galaxies, Clusters, EncodeGalaxies, EncodeClusters, UnableToRevertMachinetag
diff --git a/pymispgalaxies/api.py b/pymispgalaxies/api.py
index 6918ea4..be635c8 100644
--- a/pymispgalaxies/api.py
+++ b/pymispgalaxies/api.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 
 import json
diff --git a/setup.py b/setup.py
index 27b325a..6397cb0 100644
--- a/setup.py
+++ b/setup.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # -*- coding: utf-8 -*-
 from setuptools import setup
 
diff --git a/tests/tests.py b/tests/tests.py
index d7f24e8..576702c 100644
--- a/tests/tests.py
+++ b/tests/tests.py
@@ -25,7 +25,7 @@ class TestPyMISPGalaxies(unittest.TestCase):
             count = Counter(all_searchable)
             for k, v in count.items():
                 if v != 1:
-                    warnings.warn(f'Duplicate on {cluster.type}: {k}')
+                    warnings.warn('Duplicate on {}: {}'.format(cluster.type, k))
 
     def test_duplicates(self):
         has_duplicates = False