diff --git a/pungi/phases/pkgset/pkgsets.py b/pungi/phases/pkgset/pkgsets.py
index b15b92d3..823812ec 100644
--- a/pungi/phases/pkgset/pkgsets.py
+++ b/pungi/phases/pkgset/pkgsets.py
@@ -253,7 +253,7 @@ class PackageSetBase(kobo.log.LoggingBase):
         Saves the current FileCache using the pickle module to `file_path`.
         """
         with open(file_path, 'wb') as f:
-            pickle.dump(self.file_cache, f)
+            pickle.dump(self.file_cache, f, protocol=pickle.HIGHEST_PROTOCOL)
 
 
 class FilelistPackageSet(PackageSetBase):
diff --git a/pungi/phases/pkgset/sources/source_koji.py b/pungi/phases/pkgset/sources/source_koji.py
index b1069543..a05165e1 100644
--- a/pungi/phases/pkgset/sources/source_koji.py
+++ b/pungi/phases/pkgset/sources/source_koji.py
@@ -712,7 +712,7 @@ def populate_global_pkgset(compose, koji_wrapper, path_prefix, event):
             else:
                 global_pkgset.fast_merge(pkgset)
         with open(global_pkgset_path, 'wb') as f:
-            data = pickle.dumps(global_pkgset)
+            data = pickle.dumps(global_pkgset, protocol=pickle.HIGHEST_PROTOCOL)
             f.write(data)
 
     # write global package list
diff --git a/pungi/phases/pkgset/sources/source_repos.py b/pungi/phases/pkgset/sources/source_repos.py
index c25165f0..9d73215e 100644
--- a/pungi/phases/pkgset/sources/source_repos.py
+++ b/pungi/phases/pkgset/sources/source_repos.py
@@ -152,7 +152,7 @@ def populate_global_pkgset(compose, file_list, path_prefix):
         pkgset = pungi.phases.pkgset.pkgsets.FilelistPackageSet(compose.conf["sigkeys"], logger=compose._logger, arches=ALL_ARCHES)
         pkgset.populate(file_list)
         with open(global_pkgset_path, "wb") as f:
-            pickle.dump(pkgset, f)
+            pickle.dump(pkgset, f, protocol=pickle.HIGHEST_PROTOCOL)
 
     # write global package list
     pkgset.save_file_list(compose.paths.work.package_list(arch="global"), remove_path_prefix=path_prefix)
diff --git a/tests/test_pkgset_source_koji.py b/tests/test_pkgset_source_koji.py
index 9946a8e7..74953cb0 100644
--- a/tests/test_pkgset_source_koji.py
+++ b/tests/test_pkgset_source_koji.py
@@ -10,6 +10,8 @@ try:
 except ImportError:
     import unittest
 
+from six.moves import cPickle as pickle
+
 sys.path.insert(0, os.path.join(os.path.dirname(__file__), ".."))
 
 from pungi.phases.pkgset.sources import source_koji
@@ -127,7 +129,7 @@ class TestPopulateGlobalPkgset(helpers.PungiTestCase):
             ]
         )
         self.assertItemsEqual(pickle_dumps.call_args_list,
-                              [mock.call(orig_pkgset)])
+                              [mock.call(orig_pkgset, protocol=pickle.HIGHEST_PROTOCOL)])
         with open(self.pkgset_path) as f:
             self.assertEqual(f.read(), 'DATA')
 
@@ -174,7 +176,7 @@ class TestPopulateGlobalPkgset(helpers.PungiTestCase):
         # for each tag, call pkgset.fast_merge once for each variant and once for global pkgset
         self.assertEqual(pkgset.fast_merge.call_count, 2 * (len(self.compose.all_variants.values()) + 1))
         self.assertItemsEqual(pickle_dumps.call_args_list,
-                              [mock.call(orig_pkgset)])
+                              [mock.call(orig_pkgset, protocol=pickle.HIGHEST_PROTOCOL)])
         with open(self.pkgset_path) as f:
             self.assertEqual(f.read(), 'DATA')